L. Childress, M. P. Schmidt, A. D. Kashkanova, C. D. Brown, G. I. Harris, Andrea Aiello, Florian Marquardt, J. G. E. Harris
Physical Review A
96(6)
063842
(2017)
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We describe a proposal for a type of optomechanical system based on a drop of liquid helium that ismagnetically levitated in vacuum. In the proposed device, the drop would serve three roles: its optical whispering-gallery modes would provide the optical cavity, its surface vibrations would constitute the mechanical element, and evaporation of He atoms from its surface would provide continuous refrigeration. We analyze the feasibility of such a system in light of previous experimental demonstrations of its essential components: magnetic levitation of mm-scale and cm-scale drops of liquid He, evaporative cooling of He droplets in vacuum, and coupling to high-quality optical whispering-gallery modes in a wide range of liquids. We find that the combination of these features could result in a device that approaches the single-photon strong-coupling regime, due to the high optical quality factors attainable at low temperatures. Moreover, the system offers a unique opportunity to use optical techniques to study the motion of a superfluid that is freely levitating in vacuum (in the case of He-4). Alternatively, for a normal fluid drop of He-3, we propose to exploit the coupling between the drop's rotations and vibrations to perform quantum nondemolition measurements of angular momentum.
Multiparameter Quantum Metrology of Incoherent Point Sources: Towards Realistic Superresolution
J. Rehacek, Z. Hradil, B. Stoklasa, M. Paur, J. Grover, A. Krzic, Luis Sanchez-Soto
Physical Review A
96(6)
062107
(2017)
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We establish the multiparameter quantum Cramér-Rao bound for simultaneously estimating the centroid, the separation, and the relative intensities of two incoherent optical point sources using alinear imaging system. For equally bright sources, the Cramér-Rao bound is independent of the source separation, which confirms that the Rayleigh resolution limit is just an artifact of the<br>conventional direct imaging and can be overcome with an adequate strategy. For the general case of unequally bright sources, the amount of information one can<br>gain about the separation falls to zero, but we show that there is always a quadratic improvement in an optimal detection in comparison with the intensity measurements. This advantage can be of utmost important in realistic scenarios, such as observational astronomy.
L lines, C points and Chern numbers: understanding band structure topology using polarization fields
Thomas Fösel, Vittorio Peano, Florian Marquardt
New Journal of Physics
19
115013
(2017)
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Topology has appeared in different physical contexts. The most prominent application is topologically protected edge transport in condensed matter physics. The Chern number, the topological invariant of gapped Bloch Hamiltonians, is an important quantity in this field. Another example of topology, in polarization physics, are polarization singularities, called L lines and C points. By establishing a connection between these two theories, we develop a novel technique to visualize and potentially measure the Chern number: it can be expressed either as the winding of the polarization azimuth along L lines in reciprocal space, or in terms of the handedness and the index of the C points. For mechanical systems, this is directly connected to the visible motion patterns.
Quantum metrology at the limit with extremal Majorana constellations
F. Bouchard, P. de la Hoz, G. Bjork, R. W. Boyd, Markus Grassl, Z. Hradil, E. Karimi, A. B. Klimov, Gerd Leuchs, et al.
Quantum metrology allows for a tremendous boost in the accuracy of measurement of diverse physical parameters. The estimation of a rotation<br>constitutes a remarkable example of this quantum-enhanced precision. The recently introduced Kings of Quantumness are especially germane for this task<br>when the rotation axis is unknown, as they have a sensitivity independent of that axis and they achieve a Heisenberg-limit scaling. Here, we report the<br>experimental realization of these states by generating up to 21-dimensional orbital angular momentum states of single photons, and confirm their high metrological abilities.<br>
Fibonacci-Lucas SIC-POVMs
Markus Grassl, Andrew J. Scott
Journal of Mathematical Physics
58
122201
(2017)
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We present a conjectured family of SIC-POVMs which have an additional
symmetry group whose size is growing with the dimension. The symmetry group is
related to Fibonacci numbers, while the dimension is related to Lucas numbers.
The conjecture is supported by exact solutions for dimensions
d=4,8,19,48,124,323, as well as a numerical solution for dimension d=844.
Kinetics of CrPV and HCV IRES-mediated eukaryotic translation using single-molecule fluorescence microscopy
Olivier Bugaud, Nathalie Barbier, Helene Chommy, Nicolas Fiszman, Antoine Le Gall, David Dulin, Matthieu Saguy, Nathalie Westbrook, Karen Perronet, et al.
Protein synthesis is a complex multistep process involving many factors that need to interact in a coordinated manner to properly translate the messenger RNA. As translating ribosomes cannot be synchronized over many elongation cycles, single-molecule studies have been introduced to bring a deeper understanding of prokaryotic translation dynamics. Extending this approach to eukaryotic translation is very appealing, but initiation and specific labeling of the ribosomes are much more complicated. Here, we use a noncanonical translation initiation based on internal ribosome entry sites (IRES), and we monitor the passage of individual, unmodified mammalian ribosomes at specific fluorescent milestones along mRNA. We explore initiation by two types of IRES, the intergenic IRES of cricket paralysis virus (CrPV) and the hepatitis C (HCV) IRES, and show that they both strongly limit the rate of the first elongation steps compared to the following ones, suggesting that those first elongation cycles do not correspond to a canonical elongation. This new system opens the possibility of studying both IRES-mediated initiation and elongation kinetics of eukaryotic translation and will undoubtedly be a valuable tool to investigate the role of translation machinery modifications in human diseases.
Signatures of Nucleotide Analog Incorporation by an RNA-Dependent RNA
Polymerase Revealed Using High-Throughput Magnetic Tweezers
David Dulin, Jamie J. Arnold, Theo van Laar, Hyung-Suk Oh, Cheri Lee, Angela L. Perkins, Daniel A. Harki, Martin Depken, Craig E. Cameron, et al.
RNA viruses pose a threat to public health that is exacerbated by the dearth of antiviral therapeutics. The RNA-dependent RNA polymerase (RdRp) holds promise as a broad-spectrum, therapeutic target because of the conserved nature of the nucleotide-substrate-binding and catalytic sites. Conventional, quantitative, kinetic analysis of antiviral ribonucleotides monitors one or a few incorporation events. Here, we use a high-throughput magnetic tweezers platformto monitor the elongation dynamics of a prototypicalRdRpover thousands of nucleotide-addition cycles in the absence and presence of a suite of nucleotide analog inhibitors. We observe multiple RdRpRNA elongation complexes; only a subset of which are competent for analog utilization. Incorporation of a pyrazine-carboxamide nucleotide analog, T-1106, leads to RdRp backtracking. This analysis reveals a mechanism of action for this antiviral ribonucleotide that is corroborated by cellular studies. We propose that induced backtracking represents a distinct mechanistic class of antiviral ribonucleotides.
Tracing the phase of focused broadband laser pulses
Dominik Hoff, Michael Krüger, Lothar Maisenbacher, A. M. Sayler, Gerhard G. Paulus, Peter Hommelhoff
Nature Physics
13(10)
947-951
(2017)
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Tracing the phase of focused broadband laser pulses
Dominik Hoff, Michael Krueger, Lothar Maisenbacher, A. M. Sayler, Gerhard G. Paulus, Peter Hommelhoff
Majorization uncertainty relations are generalized for an arbitrary mixed
quantum state $\rho$ of a finite size $N$. In particular, a lower bound for the
sum of two entropies characterizing probability distributions corresponding to
measurements with respect to arbitrary two orthogonal bases is derived in terms
of the spectrum of $\rho$ and the entries of a unitary matrix $U$ relating both
bases. The obtained results can also be formulated for two measurements
performed on a single subsystem of a bipartite system described by a pure
state, and consequently expressed as uncertainty relation for the sum of
conditional entropies.
General Linearized Theory of Quantum Fluctuations around Arbitrary Limit Cycles
Carlos Navarrete-Benlloch, Talitha Weiss, Stefan Walter, Germán J. de Valcarcel
Physical Review Letters
119(13)
133601
(2017)
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The theory of Gaussian quantum fluctuations around classical steady states in nonlinear quantum-optical systems (also known as standard linearization) is a cornerstone for the analysis of such systems. Its simplicity, together with its accuracy far from critical points or situations where the nonlinearity reaches the strong coupling regime, has turned it into a widespread technique, being the first method of choice in most works on the subject. However, such a technique finds strong practical and conceptual complications when one tries to apply it to situations in which the classical long-time solution is time dependent, a most prominent example being spontaneous limit-cycle formation. Here, we introduce a linearization scheme adapted to such situations, using the driven Van der Pol oscillator as a test bed for the method, which allows us to compare it with full numerical simulations. On a conceptual level, the scheme relies on the connection between the emergence of limit cycles and the spontaneous breaking of the symmetry under temporal translations. On the practical side, the method keeps the simplicity and linear scaling with the size of the problem (number of modes) characteristic of standard linearization, making it applicable to large (many-body) systems.
Dielectric laser acceleration of sub-relativistic electrons by few-cycle laser pulses
M. Kozak, M. Foerster, J. McNeur, N. Schoenenberger, K. Leedle, H. Deng, J. S. Harris, R. L. Byer, P. Hommelhoff
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
865
84-86
(2017)
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Journal
In this paper we show the application of few-cycle infrared laser pulses for dielectric laser acceleration of electrons in the vicinity of a silicon nanostructure. An ultrashort pulse duration of 20 fs (3.3 optical cycles) allows achieving high peak fields of 2.8 GV/m without structural damage, leading to a peak acceleration gradient of G(p)=210 MeV/m for sub-relativistic electrons (v=0.33c).
Cavity Antiresonance Spectroscopy of Dipole Coupled Subradiant Arrays
David Plankensteiner, Christian Sommer, Helmut Ritsch, Claudiu Genes
An array of N closely spaced dipole coupled quantum emitters exhibits super-and subradiance with characteristic tailorable spatial radiation patterns. Optimizing the emitter geometry and distance with respect to the spatial profile of a near resonant optical cavity mode allows us to increase the ratio between light scattering into the cavity mode and free space emission by several orders of magnitude. This leads to distinct scaling of the collective coherent emitter-field coupling vs the free space decay as a function of the emitter number. In particular, for subradiant states, the effective cooperativity increases much faster than the typical linear proportional to N scaling for independent emitters. This extraordinary collective enhancement is manifested both in the amplitude and the phase profile of narrow collective antiresonances appearing at the cavity output port in transmission spectroscopy.
Unraveling beam self-healing
Andrea Aiello, Girish S. Agarwal, Martin Paur, Bohumil Stoklasa, Zdenek Hradil, Jaroslav Rehacek, Pablo de la Hoz, Gerd Leuchs, Luis L. Sanchez-Soto
Optics Express
25(16)
19147-19157
(2017)
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We show that, contrary to popular belief, diffraction-free beams not only may reconstruct themselves after hitting an opaque obstacle but also, for example, Gaussian beams. We unravel the mathematics and the physics underlying the self-reconstruction mechanism and we provide for a novel definition for the minimum reconstruction distance beyond geometric optics, which is in principle applicable to any optical beam that admits an angular spectrum representation. Moreover, we propose to quantify the self-reconstruction ability of a beam via a newly established degree of self-healing. This is defined via a comparison between the amplitudes, as opposite to intensities, of the original beam and the obstructed one. Such comparison is experimentally accomplished by tailoring an innovative experimental technique based upon Shack-Hartmann wave front reconstruction. We believe that these results can open new avenues in this field. (C) 2017 Optical Society of America
Efficient tomography with unknown detectors
L. Motka, M. Paur, J. Rehacek, Z. Hradil, L. L. Sanchez-Soto
We compare the two main techniques used for estimating the state of a
physical system from unknown measurements: standard detector tomography and
data-pattern tomography. Adopting linear inversion as a fair benchmark, we show
that the difference between these two protocols can be traced back to the
nonexistence of the reverse-order law for pseudoinverses. We capitalize on this
fact to identify regimes where the data-pattern approach outperforms the
standard one and vice versa. We corroborate these conclusions with numerical
simulations of relevant examples of quantum state tomography.
From Kardar-Parisi-Zhang scaling to explosive desynchronization in arrays of limit-cycle oscillators
Roland Lauter, Aditi Mitra, Florian Marquardt
Physical Review E
96(1)
012220
(2017)
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Phase oscillator lattices subject to noise are one of the most fundamental systems in nonequilibrium physics. We have discovered a dynamical transition which has a significant impact on the synchronization dynamics in such lattices, as it leads to an explosive increase of the phase diffusion rate by orders of magnitude. Our analysis is based on the widely applicable Kuramoto-Sakaguchi model, with local couplings between oscillators. For one-dimensional lattices, we observe the universal evolution of the phase spread that is suggested by a connection to the theory of surface growth, as described by the Kardar-Parisi-Zhang (KPZ) model. Moreover, we are able to explain the dynamical transition both in one and two dimensions by connecting it to an apparent finite-time singularity in a related KPZ lattice model. Our findings have direct consequences for the frequency stability of coupled oscillator lattices.Phase oscillator lattices subject to noise are one of the most fundamental systems in nonequilibrium physics. We have discovered a dynamical transition which has a significant impact on the synchronization dynamics in such lattices, as it leads to an explosive increase of the phase diffusion rate by orders of magnitude. Our analysis is based on the widely applicable Kuramoto-Sakaguchi model, with local couplings between oscillators. For one-dimensional lattices, we observe the universal evolution of the phase spread that is suggested by a connection to the theory of surface growth, as described by the Kardar-Parisi-Zhang (KPZ) model. Moreover, we are able to explain the dynamical transition both in one and two dimensions by connecting it to an apparent finite-time singularity in a related KPZ lattice model. Our findings have direct consequences for the frequency stability of coupled oscillator lattices.
Invariant Perfect Tensors
Youning Li, Muxin Han, Markus Grassl, Bei Zeng
New Journal of Physics
19
063029
(2017)
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Invariant tensors are states in the SU(2) tensor product representation that are invariant under the SU(2) action. They play an important role in the study of loop quantum gravity. On the other hand, perfect tensors are highly<br>entangled many-body quantum states with local density matrices maximally mixed. Recently, the notion of perfect tensors recently has attracted a lot of<br>attention in the fields of quantum information theory, condensed matter theory, and quantum gravity. In this work, we introduce the concept of an invariant perfect tensor (IPT), which is a $n$-valent tensor that is both invariant and perfect. We discuss the existence and construction of IPT. For bivalent tensors, the invariant perfect tensor is the unique singlet state for each local dimension. The trivalent invariant perfect tensor also exists and is uniquely given by Wigner's 3j symbol. However, we show that, surprisingly, there does not exist four-valent invariant perfect tensors for any dimension. On the contrary, when the dimension is large, almost all invariant tensors are perfect asymptotically, which is a consequence of the phenomenon of<br>concentration of measure for multipartite quantum states.
Probing the salt dependence of the torsional stiffness of DNA by multiplexed magnetic torque tweezers
Franziska Kriegel, Niklas Ermann, Ruaridh Forbes, David Dulin, Nynke H. Dekker, Jan Lipfert
Nucleic Acids Research
45(10)
5920-5929
(2017)
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Journal
The mechanical properties of DNA fundamentally constrain and enable the storage and transmission of genetic information and its use in DNA nanotechnology. Many properties of DNA depend on the ionic environment due to its highly charged backbone. In particular, both theoretical analyses and direct single-molecule experiments have shown its bending stiffness to depend on salt concentration. In contrast, the salt-dependence of the twist stiffness of DNA is much less explored. Here, we employ optimized multiplexed magnetic torque tweezers to study the torsional stiffness of DNA under varying salt conditions as a function of stretching force. At low forces (< 3 pN), the effective torsional stiffness is similar to 10% smaller for high salt conditions (500 mM NaCl or 10 mM MgCl2) compared to lower salt concentrations (20 mM NaCl and 100 mM NaCl). These differences, however, can be accounted for by taking into account the known salt dependence of the bending stiffness. In addition, the measured high-force (6.5 pN) torsional stiffness values of C = 103 +/- 4 nm are identical, within experimental errors, for all tested salt concentration, suggesting that the intrinsic torsional stiffness of DNA does not depend on salt.
Towards optimal quantum tomography with unbalanced homodyning
Yong Siah Teo, Hyunseok Jeong, Luis L. Sanchez-Soto
Balanced homodyning, heterodyning and unbalanced homodyning are the three
well-known sampling techniques used in quantum optics to characterize all
possible photonic sources in continuous-variable quantum information theory. We
show that for all quantum states and all observable-parameter tomography
schemes, which includes the reconstructions of arbitrary operator moments and
phase-space quasi-distributions, localized sampling with unbalanced homodyning
is always tomographically more powerful (gives more accurate estimators) than
delocalized sampling with heterodyning. The latter is recently known to often
give more accurate parameter reconstructions than conventional marginalized
sampling with balanced homodyning. This result also holds for realistic
photodetectors with subunit efficiency. With examples from first- through
fourth-moment tomography, we demonstrate that unbalanced homodyning can
outperform balanced homodyning when heterodyning fails to do so. This new
benchmark takes us one step towards optimal continuous-variable tomography with
conventional photodetectors and minimal experimental components.
Synchronization of an optomechanical system to an external drive
Ehud Amitai, Niels Loerch, Andreas Nunnenkamp, Stefan Walter, Christoph Bruder
Physical Review A
95(5)
053858
(2017)
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Optomechanical systems driven by an effective blue-detuned laser can exhibit self-sustained oscillations of the mechanical oscillator. These self-oscillations are a prerequisite for the observation of synchronization. Here, we study the synchronization of the mechanical oscillations to an external reference drive. We study two cases of reference drives: (1) an additional laser applied to the optical cavity; (2) a mechanical drive applied directly to the mechanical oscillator. Starting from a master equation description, we derive a microscopic Adler equation for both cases, valid in the classical regime in which the quantum shot noise of the mechanical self-oscillator does not play a role. Furthermore, we numerically show that, in both cases, synchronization arises also in the quantum regime. The optomechanical system is therefore a good candidate for the study of quantum synchronization.
Focusing characteristics of a 4 pi parabolic mirror light-matter interface
Lucas Alber, Martin Fischer, Marianne Bader, Klaus Mantel, Markus Sondermann, Gerd Leuchs
JOURNAL OF THE EUROPEAN OPTICAL SOCIETY-RAPID PUBLICATIONS
13
14
(2017)
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Background: Focusing with a 4 pi parabolic mirror allows for concentrating light from nearly the complete solid angle, whereas focusing with a single microscope objective limits the angle cone used for focusing to half solid angle at maximum. Increasing the solid angle by using deep parabolic mirrors comes at the cost of adding more complexity to the mirror's fabrication process and might introduce errors that reduce the focusing quality.
Methods: To determine these errors, we experimentally examine the focusing properties of a 4p parabolic mirror that was produced by single-point diamond turning. The properties are characterized with a single Yb-174(+) ion as a mobile point scatterer. The ion is trapped in a vacuum environment with a movable high optical access Paul trap.
Results: We demonstrate an effective focal spot size of 209 nm in lateral and 551 nm in axial direction. Such tight focusing allows us to build an efficient light-matter interface.
Conclusion: Our findings agree with numerical simulations incorporating a finite ion temperature and interferometrically measured wavefront aberrations induced by the parabolic mirror. We point at further technological improvements and discuss the general scope of applications of a 4p parabolic mirror.
Quantum-coherent phase oscillations in synchronization
Talitha Weiss, Stefan Walter, Florian Marquardt
Physical Review A
95(4)
041802
(2017)
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Recently, several studies have investigated synchronization in quantum-mechanical limit-cycle oscillators. However, the quantum nature of these systems remained partially hidden, since the dynamics of the oscillator's phase was overdamped and therefore incoherent. We show that there exist regimes of underdamped and even quantum-coherent phase motion, opening up new possibilities to study quantum synchronization dynamics. To this end, we investigate the Van der Pol oscillator (a paradigm for a self-oscillating system) synchronized to an external drive. We derive an effective quantum model which fully describes the regime of underdamped phase motion and additionally allows us to identify the quality of quantum coherence. Finally, we identify quantum limit cycles of the phase itself.
Many-Particle Dephasing after a Quench
Thomas Kiendl, Florian Marquardt
Physical Review Letters
118(13)
130601
(2017)
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After a quench in a quantum many-body system, expectation values tend to relax towards long-time averages. However, temporal fluctuations remain in the long-time limit, and it is crucial to study the suppression of these fluctuations with increasing system size. The particularly important case of nonintegrable models has been addressed so far only by numerics and conjectures based on analytical bounds. In this work, we are able to derive analytical predictions for the temporal fluctuations in a nonintegrable model (the transverse Ising chain with extra terms). Our results are based on identifying a dynamical regime of "many-particle dephasing,"where quasiparticles do not yet relax but fluctuations are nonetheless suppressed exponentially by weak integrability breaking.
Label-free optical detection of single enzyme-reactant reactions and associated conformational changes
Eugene Kim, Martin D. Baaske, Isabel Schuldes, Peter S. Wilsch, Frank Vollmer
Monitoring the kinetics and conformational dynamics of single enzymes is crucial to better understand their biological functions because these motions and structural dynamics are usually unsynchronized among the molecules. However, detecting the enzyme-reactant interactions and associated conformational changes of the enzyme on a single-molecule basis remains as a challenge to established optical techniques because of the commonly required labeling of the reactants or the enzyme itself. The labeling process is usually nontrivial, and the labels themselves might skew the physical properties of the enzyme. We demonstrate an optical, label-free method capable of observing enzymatic interactions and associated conformational changes on a single-molecule level. We monitor polymerase/DNA interactions via the strong near-field enhancement provided by plasmonic nanorods resonantly coupled to whispering gallery modes in microcavities. Specifically, we use two different recognition schemes: one in which the kinetics of polymerase/DNA interactions are probed in the vicinity of DNA-functionalized nanorods, and the other in which these interactions are probed via the magnitude of conformational changes in the polymerase molecules immobilized on nanorods. In both approaches, we find that low and high polymerase activities can be clearly discerned through their characteristic signal amplitude and signal length distributions. Furthermore, the thermodynamic study of the monitored interactions suggests the occurrence of DNA polymerization. This work constitutes a proof-of-concept study of enzymatic activities using plasmonically enhanced microcavities and establishes an alternative and label-free method capable of investigating structural changes in single molecules.
Pseudomagnetic fields for sound at the nanoscale
Christian Brendel, Vittorio Peano, Oskar J. Painter, Florian Marquardt
Proceedings of the National Academy of Sciences of the United States of America
114(17)
E3390-E3395
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There is a growing effort in creating chiral transport of sound waves. However, most approaches so far have been confined to the macroscopic scale. Here, we propose an approach suitable to the nanoscale that is based on pseudomagnetic fields. These pseudomagnetic fields for sound waves are the analogue of what electrons experience in strained graphene. In our proposal, they are created by simple geometrical modifications of an existing and experimentally proven phononic crystal design, the snowflake crystal. This platform is robust, scalable, and well-suited for a variety of excitation and readout mechanisms, among them optomechanical approaches.
Towards next-generation label-free biosensors: recent advances in whispering gallery mode sensors
Whispering gallery mode biosensors have been widely exploited over the past decade to study molecular interactions by virtue of their high sensitivity and applicability in real-time kinetic analysis without the requirement to label. There have been immense research efforts made for advancing the instrumentation as well as the design of detection assays, with the common goal of progressing towards real-world sensing applications. We therefore review a set of recent developments made in this field and discuss the requirements that whispering gallery mode label-free sensors need to fulfill for making a real world impact outside of the laboratory. These requirements are directly related to the challenges that these sensors face, and the methods proposed to overcome them are discussed. Moving forward, we provide the future prospects and the potential impact of this technology.
Coarse graining the phase space of N qubits
Olivia Di Matteo, Luis Sanchez-Soto, Gerd Leuchs, Markus Grassl
Physical Review A
95(2)
022340
(2017)
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We develop a systematic coarse graining procedure for systems of N qubits. We exploit the underlying geometrical structures of the associated discrete<br>phase space to produce a coarse-grained version with reduced effective size. Our coarse-grained spaces inherit key properties of the original ones. In<br>particular, our procedure naturally yields a subset of the original measurement operators, which can be used to construct a coarse discrete Wigner function. These operators also constitute a systematic choice of incomplete measurements for the tomographer wishing to probe an intractably large system.
Significant performance enhancement of InGaN/GaN nanorod LEDs with multi-layer graphene transparent electrodes by alumina surface passivation
Michael Latzel, P. Buettner, George Sarau, Katja Höflich, Martin Heilmann, W. Chen, X. Wen, G. Conibeer, Silke Christiansen
Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 nm alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.
Cryogenic optical localization provides 3D protein structure data with Angstrom resolution
Siegfried Weisenburger, Daniel Boening, Benjamin Schomburg, Karin Giller, Stefan Becker, Christian Griesinger, Vahid Sandoghdar
We introduce Cryogenic Optical Localization in 3D (COLD), a method to localize multiple fluorescent sites within a single small protein with Angstrom resolution. We demonstrate COLD by determining the conformational state of the cytosolic Per-ARNT-Sim domain from the histidine kinase CitA of Geobacillus thermodenitnficans and resolving the four biotin sites of streptavidin. COLD provides quantitative 3D information about small- to medium-sized biomolecules on the Angstrom scale and complements other techniques in structural biology.
High visibility in two-color above-threshold photoemission from tungsten nanotips in a coherent control scheme
Timo Paschen, Michael Förster, Michael Krüger, Christoph Lemell, Georg Wachter, Florian Libisch, Thomas Madlener, Joachim Burgdoerfer, Peter Hommelhoff
JOURNAL OF MODERN OPTICS
64(10-11)
1054-1060
(2017)
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Journal
In this article, we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between fundamental (1560nm) and second harmonic (780nm) pulses of a femtosecond fiber laser at the nanotip, electron emission is significantly enhanced or depressed during temporal overlap. Electron emission is studied as a function of pulse delay, optical near-field intensities, DC bias field and final photoelectron energy. Under optimized conditions modulation amplitudes of the electron emission of 97.5% are achieved. Experimental observations are discussed in the framework of quantum-pathway interference supported by local density of states simulations.
Optical gating and streaking of free electrons with sub-optical cycle precision
M. Kozak, J. McNeur, K. J. Leedle, H. Deng, N. Schoenenberger, A. Ruehl, I. Hartl, J. S. Harris, R. L. Byer, et al.
The temporal resolution of ultrafast electron diffraction and microscopy experiments is currently limited by the available experimental techniques for the generation and characterization of electron bunches with single femtosecond or attosecond durations. Here, we present proof of principle experiments of an optical gating concept for free electrons via direct time-domain visualization of the sub-optical cycle energy and transverse momentum structure imprinted on the electron beam. We demonstrate a temporal resolution of 1.2 +/- 0.3 fs. The scheme is based on the synchronous interaction between electrons and the near-field mode of a dielectric nano-grating excited by a femtosecond laser pulse with an optical period duration of 6.5 fs. The sub-optical cycle resolution demonstrated here is promising for use in laser-driven streak cameras for attosecond temporal characterization of bunched particle beams as well as time-resolved experiments with free-electron beams.
Small sets of complementary observables
Markus Grassl, D. McNulty, L. Mišta, T. Paterek
Physical Review A
95(1)
012118
(2017)
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Two observables are called complementary if preparing a physical object in an eigenstate of one of them yields a completely random result in a measurement of<br>the other. We investigate small sets of complementary observables that cannot be extended by yet another complementary observable. We construct explicit<br>examples of the unextendible sets up to dimension $16$ and conjecture certain small sets to be unextendible in higher dimensions. Our constructions provide<br>three complementary measurements, only one observable away from the ultimate minimum of two observables in the set. Almost all of our examples in finite dimension allow to discriminate pure states from some mixed states, and shed light on the complex topology of the Bloch space of higher-dimensional quantum systems.<br>
Shifting the phase of a coherent beam with a Yb-174(+) ion: influence of the scattering cross section
Martin Fischer, Bharath Srivathsan, Lucas Alber, Markus Weber, Markus Sondermann, Gerd Leuchs
APPLIED PHYSICS B-LASERS AND OPTICS
123(1)
48
(2017)
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We discuss and measure the phase shift imposed onto a radially polarized light beam when focusing it onto an Yb-174(+) ion. In the derivation of the expected phase shifts, we include the properties of the involved atomic levels. Furthermore, we emphasize the importance of the scattering cross section and its relation to the efficiency for coupling the focused light to an atom. The phase shifts found in the experiment are compatible with the expected ones when accounting for known deficiencies of the focusing optics and the motion of the trapped ion at the Doppler limit of laser cooling (Hensch and Schawlow in Opt Commun 13:68-69,1975).
Generalized non-reciprocity in an optomechanical circuit via synthetic magnetism and reservoir engineering
Kejie Fang, Jie Luo, Anja Metelmann, Matthew H. Matheny, Florian Marquardt, Aashish A. Clerk, Oskar Painter
Synthetic magnetism has been used to control charge neutral excitations for applications ranging from classical beam steering to quantum simulation. In optomechanics, radiation-pressure-induced parametric coupling between optical (photon) and mechanical (phonon) excitations may be used to break time-reversal symmetry, providing the prerequisite for synthetic magnetism. Here we design and fabricate a silicon optomechanical circuit with both optical and mechanical connectivity between two optomechanical cavities. Driving the two cavities with phase-correlated laser light results in a synthetic magnetic flux, which, in combination with dissipative coupling to the mechanical bath, leads to non-reciprocal transport of photons with 35 dB of isolation. Additionally, optical pumping with blue-detuned light manifests as a particle non-conserving interaction between photons and phonons, resulting in directional optical amplification of 12 dB in the isolator through-direction. These results suggest the possibility of using optomechanical circuits to create a more general class of non-reciprocal optical devices, and further, to enable new topological phases for both light and sound on a microchip.
Anderson localization of composite excitations in disordered optomechanical arrays
Thales Figueiredo Roque, Vittorio Peano, Oleg M. Yevtushenko, Florian Marquardt
New Journal of Physics
19
013006
(2017)
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Journal
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PDF
Optomechanical (OMA) arrays are a promising future platform for studies of transport, many-body dynamics, quantum control and topological effects in systems of coupled photon and phonon modes. We introduce disordered OMA arrays, focusing on features of Anderson localization of hybrid photon-phonon excitations. It turns out that these represent a unique disordered system, where basic parameters can be easily controlled by varying the frequency and the amplitude of an external laser field. We show that the two-species setting leads to a non-trivial frequency dependence of the localization length for intermediate laser intensities. This could serve as a convincing evidence of localization in a non-equilibrium dissipative situation.
Analytical formulation for the bend loss in single-ring hollow-core photonic crystal fibers
Michael H. Frosz, Paul Roth, Mehmet C. Guenendi, Philip St. J. Russell
Understanding bend loss in single-ring hollow-core photonic crystal fibers (PCFs) is becoming of increasing importance as the fibers enter practical applications. While purely numerical approaches are useful, there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss. We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum, and that this can be calculated from the structural parameters of a fiber using a simple analytical formula. This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength. It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure. (C) 2017 Chinese Laser Press
Numerical and experimental analysis of polarization dependent gain
vector in Brillouin amplification system
Shan Cao, Shangran Xie, Fei Liu, Xiaoping Zheng, Min Zhang
The polarization dependent gain (PDG) of Brillouin amplification systems is numerically investigated in detail by solving a new model describing the evolution of PDG vector along the fiber with random birefringence. In this model both the modulus and orientation of the PDG vector are considered. By including the temporal distribution of fiber birefringence, the statistical properties of the PDG vector, including its mean value and standard deviation, are presented as function of fiber beat length, input pump power and fiber length, which can be directly applied in practice to estimate the performance of Brillouin amplification systems in term of its polarization dependence. Experimental results on a Brillouin amplification system are also reported to support the validity of our model. The analysis presented here helps to gain insight for the properties of PDG vector in any SBS systems.
A single molecule as a high-fidelity photon gun for producing
intensity-squeezed light
Xiao-Liu Chu, Stephan Goetzinger, Vahid Sandoghdar
A two-level atom cannot emit more than one photon at a time. As early as the 1980s, this quantum feature was identified as a gateway to 'single-photon sources', where a regular excitation sequence would create a stream of light particles with photon number fluctuations below the shot noise(1). Such an intensity-squeezed beam of light would be desirable for a range of applications, such as quantum imaging, sensing, enhanced precision measurements and information processing(2,3). However, experimental realizations of these sources have been hindered by large losses caused by low photon-collection efficiencies and photophysical shortcomings. By using a planar metallodielectric antenna applied to an organic molecule, we demonstrate the most regular stream of single photons reported to date. The measured intensity fluctuations were limited by our detection efficiency and amounted to 2.2 dB squeezing.
Generation of microjoule pulses in the deep ultraviolet at megahertz repetition rates
Felix Koettig, Francesco Tani, Christian Martens-Biersach, John C. Travers, Philip St J. Russell
Although ultraviolet (UV) light is important in many areas of science and technology, there are very few if any lasers capable of delivering wavelength-tunable ultrashort UV pulses at high repetition rates. Here we report the generation of deep UV laser pulses at megahertz repetition rates and microjoule energies by means of dispersive wave (DW) emission from self-compressed solitons in gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF). Pulses from an ytterbium fiber laser (similar to 300 fs) are first compressed to <25 fs in a SR-PCF-based nonlinear compression stage and subsequently used to pump a second SR-PCF stage for broadband DW generation in the deep UV. The UV wavelength is tunable by selecting the gas species and the pressure. Through rigorous optimization of the system, in particular employing a large-core fiber filled with light noble gases, we achieve 1 mu J pulse energies in the deep UV, which is more than 10 times higher, at average powers more than four orders of magnitude greater (reaching 1 W) than previously demonstrated, with only 20 mu J pulses from the pump laser. (C) 2017 Optical Society of America
Plasmonic gold helices for the visible range fabricated by oxygen plasma purification of electron beam induced deposits
Caspar Haverkamp, Katja Hoeflich, Sara Jaeckle, Anna Manzoni, Silke Christiansen
Electron beam induced deposition (EBID) currently provides the only direct writing technique for truly three-dimensional nanostructures with geometrical features below 50 nm. Unfortunately, the depositions from metal-organic precursors suffer from a substantial carbon content. This hinders many applications, especially in plasmonics where the metallic nature of the geometric surfaces is mandatory. To overcome this problem a post-deposition treatment with oxygen plasma at room temperature was investigated for the purification of gold containing EBID structures. Upon plasma treatment, the structures experience a shrinkage in diameter of about 18 nm but entirely keep their initial shape. The proposed purification step results in a core-shell structure with the core consisting of mainly unaffected EBID material and a gold shell of about 20 nm in thickness. These purified structures are plasmonically active in the visible wavelength range as shown by dark field optical microscopy on helical nanostructures. Most notably, electromagnetic modeling of the corresponding scattering spectra verified that the thickness and quality of the resulting gold shell ensures an optical response equal to that of pure gold nanostructures.
We introduce a novel design of anti-resonant fibers with negative-curvature square cores to be employed in 1.55 and 2.94 mu m transmission bands. The fibers have low losses and single-mode operation via optimizing the negative curvature of the guiding walls. The first proposed fiber shows a broadband transmission window spanning 0.9-1.7 mu m, with losses of 0.025 and 0.056 dB/m at 1.064 and 1.55 mu m, respectively. The second proposed fiber has approximately a 0.023 dB/m guiding loss at 2.94 mu m with a small cross-sectional area, useful for laser micromachining applications. (C) 2017 Optical Society of America
Cathodoluminescence spectroscopy is a key analysis technique in nanophotonics research and technology, yet many aspects of its fundamental excitation mechanisms are not well understood on the single-electron and single-photon level. Here, we determine the cathodoluminescence emission statistics of InGaN quantum wells embedded in GaN under 6-30-keV electron excitation and find that the light emission rate varies strongly from electron to electron. Strong photon bunching is observed for the InGaN quantum well emission at 2.77 eV due to the generation of multiple quantum well excitations by a single primary electron. The bunching effect, measured by the g((2))(t) autocorrelation function, decreases with increasing beam current in the range 3-350 pA. Under pulsed excitation (p = 2-100 ns; 0.13-6 electrons per pulse), the bunching effect strongly increases. A model based on Monte Carlo simulations is developed that assumes a fraction gamma of the primary electrons generates electron-hole pairs that create multiple photons in the quantum wells. At a fixed primary electron energy (10 keV) the model explains all g(2) measurements for different beam currents and pulse durations using a single value for gamma= 0.5. At lower energies, when electrons cause mostly near-surface excitations, gamma is reduced (gamma = 0.01 at 6 keV), which is explained by the presence of a AlGaN barrier layer that inhibits carrier diffusion to the buried quantum wells. The combination of g((2)) measurements in pulsed and continuous mode with spectral analysis provides a powerful tool to study optoelectronic properties and may find application in many other optically active systems and devices.
Fresnel-Reflection-Free Self-Aligning Nanospike Interface between a Step-Index Fiber and a Hollow-Core Photonic-Crystal-Fiber Gas Cell
Riccardo Pennetta, Shangran Xie, Frances Lenahan, Manoj Mridha, David Novoa, Philip St. J. Russell
We report a fully integrated interface delivering efficient, reflection-free, single-mode, and self-aligned coupling between a step-index fiber and a gas-filled hollow-core photonic crystal fiber. The device offers a universal solution for interfacing solid and hollow cores and can be sealed to allow operation either evacuated or at high pressure. Stimulated Raman scattering and molecular modulation of light are demonstrated in a H-2-filled hollow-core photonic crystal fiber using the device.
Generic method for lossless generation of arbitrarily shaped photons
We put forward a generic method that enables lossless generation of pure single photons with arbitrary shape over any degree of freedom or several degrees of freedom simultaneously. The method exploits pairs of entangled photons. One of the photons is the subject for lossy shaping manipulations followed by a specially designed mode-equalizing measurement. A successful measurement outcome heralds the losslessly shaped second photon. The method has three crucial ingredients that define the quantum state of the shaped photon: the initial bipartite state of the photons, modulation of the first photon, and its mode-equalizing detection. We provide a specific recipe with a combination of these ingredients for achieving any desired pure state of the shaped photon.
Generation of unipolar half-cycle pulses via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer
M. V. Arkhipov, R. M. Arkhipov, A. V. Pakhomov, I. V. Babushkin, A. Demircan, U. Morgner, N. N. Rosanov
We propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse from a thin flat metallic or dielectric layer. Unipolar pulses in reflection arise due to specifics of one-dimensional pulse propagation. Namely, we show that the field emitted by the layer is proportional to the velocity of the oscillating charges in the medium, instead of their acceleration. Besides, the oscillation velocity of the charges can be forced to keep a constant sign throughout the pulse duration. That is, reflection of ultrashort pulses from broad-area layers with nanometer-scale thickness can be very different from the common reflection in the case of longer pulses and thicker layers. This suggests a possibility of unusual transformations of few-cycle light pulses in completely linear optical systems. (C) 2017 Optical Society of America
Coherent Coupling of a Single Molecule to a Scanning Fabry-Perot
Microcavity
Daqing Wang, Hrishikesh Kelkar, Diego-Martin Cano, Tobias Utikal, Stephan Goetzinger, Vahid Sandoghdar
Organic dye molecules have been used in a great number of scientific and technological applications, but their wider use in quantum optics has been hampered by transitions to short-lived vibrational levels, which limit their coherence properties. To remedy this, one can take advantage of optical resonators. Here, we present the first results on coherent molecule-resonator coupling, where a single polycyclic aromatic hydrocarbon molecule extinguishes 38% of the light entering a microcavity at liquid helium temperature. We also demonstrate fourfold improvement of single-molecule stimulated emission compared to free-space focusing and take first steps for coherent mechanical manipulation of the molecular transition. Our approach of coupling molecules to an open and tunable microcavity with a very low mode volume and moderately low quality factors of the order of 10(3) paves the way for the realization of nonlinear and collective quantum optical effects.
Phase sensitivity of gain-unbalanced nonlinear interferometers
Enno Giese, Samuel Lemieux, Mathieu Manceau, Robert Fickler, Robert W. Boyd
The phase uncertainty of an unseeded nonlinear interferometer, where the output of one nonlinear crystal is transmitted to the input of a second crystal that analyzes it, is commonly said to be below the shot-noise level but highly dependent on detection and internal loss. Unbalancing the gains of the first (source) and second (analyzer) crystals leads to a configuration that is tolerant against detection loss. However, in terms of sensitivity, there is no advantage in choosing a stronger analyzer over a stronger source, and hence the comparison to a shot-noise level is not straightforward. Internal loss breaks this symmetry and shows that it is crucial whether the source or analyzer is dominating. Based on these results, claiming a Heisenberg scaling of the sensitivity is more subtle than in a balanced setup.
Strong plasmonic enhancement of biexciton emission: controlled coupling of a single quantum dot to a gold nanocone antenna
Korenobu Matsuzaki, Simon Vassant, Hsuan-Wei Liu, Anke Dutschke, Bjoern Hoffmann, Xuewen Chen, Silke Christiansen, Matthew R. Buck, Jennifer A. Hollingsworth, et al.
Multiexcitonic transitions and emission of several photons per excitation comprise a very attractive feature of semiconductor quantum dots for optoelectronics applications. However, these higher-order radiative processes are usually quenched in colloidal quantum dots by Auger and other nonradiative decay channels. To increase the multiexcitonic quantum efficiency, several groups have explored plasmonic enhancement, so far with moderate results. By controlled positioning of individual quantum dots in the near field of gold nanocone antennas, we enhance the radiative decay rates of monoexcitons and biexcitons by 109 and 100 folds at quantum efficiencies of 60 and 70%, respectively, in very good agreement with the outcome of numerical calculations. We discuss the implications of our work for future fundamental and applied research in nano-optics.
Phase-Insensitive Scattering of Terahertz Radiation
Mihail Petev, Niclas Westerberg, Eleonora Rubino, Daniel Moss, Arnaud Couairon, Francois Legare, Roberto Morandotti, Daniele Faccio, Matteo Clerici
The nonlinear interaction between Near-Infrared (NIR) and Terahertz pulses is principally investigated as a means for the detection of radiation in the hardly accessible THz spectral region. Most studies have targeted second-order nonlinear processes, given their higher efficiencies, and only a limited number have addressed third-order nonlinear interactions, mainly investigating four-wave mixing in air for broadband THz detection. We have studied the nonlinear interaction between THz and NIR pulses in solid-state media (specifically diamond), and we show how the former can be frequency-shifted up to UV frequencies by the scattering from the nonlinear polarisation induced by the latter. Such UV emission differs from the well-known electric field-induced second harmonic (EFISH) one, as it is generated via a phase-insensitive scattering, rather than a sum- or difference-frequency four-wave-mixing process.
Theory of metasurface based perfect absorbers
Rasoul Alaee, Mohammad Albooyeh, Carsten Rockstuhl
JOURNAL OF PHYSICS D-APPLIED PHYSICS
50(50)
503002
(2017)
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Journal
Based on an analytic approach, we present a theoretical review on the absorption, scattering, and extinction of both dipole scatterers and regular arrays composed of such scatterers i.e. metasurfaces. Besides offering a tutorial by outlining the maximum absorption limit for electrically/magnetically resonant dipole particles/metasurfaces, we give an educative analytical approach to their analysis. Moreover, we put forward the analysis of two known alternatives in providing perfect absorbers out of electrically and or magnetically resonant metasurfaces; one is based on the simultaneous presence of both electric and magnetic responses in so called Huygens metasurfaces while the other is established upon the presence of a back reflector in so called Salisbury absorbers. Our work is supported by several numerical examples to clarify the discussions in each stage.
Chip-Based All-Optical Control of Single Molecules Coherently Coupled to a Nanoguide
Pierre Tuerschmann, Nir Rotenberg, Jan Renger, Irina Harder, Olga Lohse, Tobias Utikal, Stephan Goetzinger, Vahid Sandoghdar
The feasibility of many proposals in nano quantum-optics depends on the efficient coupling of photons to individual quantum emitters, the possibility to control this interaction on demand, and the scalability of the experimental platform. To address these issues, we report on chip-based systems made of one-dimensional subwavelength dielectric waveguides (nanoguides) and polycyclic aromatic hydrocarbon molecules. We discuss the design and fabrication requirements, present data on extinction spectroscopy of single molecules coupled to a nanoguide mode, and show how an external optical beam can switch the propagation of light via a nonlinear optical process. The presented architecture paves the way for the investigation of many-body phenomena and polaritonic states and can be readily extended to more complex geometries for the realization of quantum integrated photonic circuits.
Generation of broadband mid-IR and UV light in gas-filled single-ring hollow-core PCF
Marco Cassataro, David Novoa, Mehmet C. Guenendi, Nitin N. Edavalath, Michael H. Frosz, John C. Travers, Philip St. J. Russell
We report generation of an ultrafast supercontinuum extending into the mid-infrared in gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF) pumped by 1.7 mu m light from an optical parametric amplifier. The simple fiber structure offers shallow dispersion and flat transmission in the near and mid-infrared, enabling the generation of broadband spectra extending from 270 nm to 3.1 mu m, with a total energy of a few mu J. In addition, we demonstrate the emission of ultraviolet dispersive waves whose frequency can be tuned simply by adjusting the pump wavelength. SR-PCF thus constitutes an effective means of compressing and delivering tunable ultrafast pulses in the near and mid-infrared spectral regions. (C) 2017 Optical Society of America
Flexible femtosecond inscription of fiber Bragg gratings by an optimized deformable mirror
Thorsten A. Goebel, Christian Voigtlaender, Ria G. Kraemer, Daniel Richter, Maximilian Heck, Malte P. Siems, Christian Matzdorf, Claudia Reinlein, Michael Appelfelder, et al.
The period of fiber Bragg gratings is adapted by shaping the wavefronts of ultrashort laser pulses applied in a phase mask inscription technique. A specially designed deformable mirror, based on a dielectric substrate to withstand high peak powers, is utilized to deform the wavefront. A shift of about 11 nm is demonstrated for a Bragg wavelength around 1550 nm. (c) 2017 Optical Society of America
Generation of spectral clusters in a mixture of noble and Raman-active
gases (vol 41, pg 5543, 2016)
Pooria Hosseini, Amir Abdolvand, Philip St. J. Russell
We derive two general complementarity relations for the distinguishability and visibility of genuine vector-light quantum fields in double-pinhole photon interference involving polarization modulation. The established framework reveals an intrinsic aspect of wave-particle duality of the photon, not previously reported, thus providing deeper insights into foundational quantum interference physics.
Plasmon coherence determination by nanoscattering
Yahong Chen, Andreas Norrman, Sergey A. Ponomarenko, Ari T. Friberg
We present a simple and robust protocol to recover the second-order field correlations of polychromatic, statistically stationary surface plasmon polaritons (SPPs) from a spectrum measurement in the far zone of a dipolar nanoscatterer. The recovered correlations carry comprehensive information about the spectral, spatial, and temporal coherence of the SPPs. We also introduce and exemplify for the first time, to the best of our knowledge, the two-point Stokes parameters associated with partially coherent SPP fields. (C) 2017 Optical Society of America
Fundamental precision limit of a Mach-Zehnder interferometric sensor
when one of the inputs is the vacuum
Masahiro Takeoka, Kaushik P. Seshadreesan, Chenglong You, Shuro Izumi, Jonathan P. Dowling
In the lore of quantum metrology, one often hears (or reads) the following no-go theorem: If you put a vacuum into one input port of a balanced Mach-Zehnder interferometer, then no matter what you put into the other input port, and nomatter what your detection scheme, the sensitivity can never be better than the shot-noise limit (SNL). Often the proof of this theorem is cited to be inC. Caves, Phys. Rev. D23, 1693 (1981), but upon further inspection, no such claim is made there. Quantum-Fisher-information-based arguments suggestive of this no-go theorem appear elsewhere in the literature, but are not stated in their full generality. Here we thoroughly explore this no-go theorem and give a rigorous statement: the no-go theorem holds whenever the unknown phase shift is split between both of the arms of the interferometer, but remarkably does not hold when only one arm has the unknown phase shift. In the latter scenario, we provide an explicit measurement strategy that beats the SNL. We also point out that these two scenarios are physically different and correspond to different types of sensing applications.
Acceleration of sub-relativistic electrons with an evanescent optical
wave at a planar interface
M. Kozak, P. Beck, H. Deng, J. McNeur, N. Schoenenberger, C. Gaida, F. Stutzki, M. Gebhardt, J. Limpert, et al.
We report on a theoretical and experimental study of the energy transfer between an optical evanescent wave, propagating in vacuum along the planar boundary of a dielectric material, and a beam of sub-relativistic electrons. The evanescent wave is excited via total internal reflection in the dielectric by an infrared (lambda = 2 mu m) femtosecond laser pulse. By matching the electron propagation velocity to the phase velocity of the evanescent wave, energy modulation of the electron beam is achieved. A maximum energy gain of 800 eV is observed, corresponding to the absorption of more than 1000 photons by one electron. The maximum observed acceleration gradient is 19 +/- 2 MeV/m. The striking advantage of this scheme is that a structuring of the acceleration element's surface is not required, enabling the use of materials with high laser damage thresholds that are difficult to nano-structure, such as SiC, Al2O3 or CaF2. (C) 2017 Optical Society of America
Universality of Coherent Raman Gain Suppression in Gas-Filled Broadband-Guiding Photonic Crystal Fibers
Pooria Hosseini, M. K. Mridha, D. Novoa, A. Abdolvand, P. St. J. Russell
As shown in the early 1960s, the gain in stimulated Raman scattering (SRS) is drastically suppressed when the rate of creation of phonons (via a pump-to-Stokes conversion) is exactly balanced by the rate of phonon annihilation (via a pump-to-anti-Stokes conversion). This occurs when the phonon coherence waves-synchronized vibrations of a large population of molecules-have identical propagation constants for both processes; i. e., they are phase-velocity matched. As recently demonstrated, hydrogen-filled photonic crystal fiber pumped in the vicinity of its zero-dispersion wavelength provides an ideal system for observing this effect. Here we report that Raman gain suppression is actually a universal feature of SRS in gas-filled hollow-core fibers and that it can strongly impair SRS even when the phase mismatch is high, particularly at high pump powers when it is normally assumed that nonlinear processes become more (not less) efficient. This counterintuitive result means that intermodal stimulated Raman scattering (for example, between LP01 and LP11 core modes) begins to dominate at high power levels. The results reported have important implications for fiber-based Raman shifters, amplifiers, or frequency combs, especially for operation in the ultraviolet, where the Raman gain is much higher.
Low temperature solid-state wetting and formation of nanowelds in silver nanowires
Vuk V. Radmilovic, Manuela Goebelt, Colin Ophus, Silke Christiansen, Erdmann Spiecker, Velimir R. Radmilovic
This article focuses on the microscopic mechanism of thermally induced nanoweld formation between silver nanowires (AgNWs) which is a key process for improving electrical conductivity in NW networks employed for transparent electrodes. Focused ion beam sectioning and transmission electron microscopy were applied in order to elucidate the atomic structure of a welded NW including measurement of the wetting contact angle and characterization of defect structure with atomic accuracy, which provides fundamental information on the welding mechanism. Crystal lattice strain, obtained by direct evaluation of atomic column displacements in high resolution scanning transmission electron microscopy images, was shown to be non-uniform among the five twin segments of the AgNW pentagonal structure. It was found that the pentagonal cross-sectional morphology of AgNWs has a dominant effect on the formation of nanowelds by controlling initial wetting as well as diffusion of Ag atoms between the NWs. Due to complete solid-state wetting, at an angle of similar to 4.8 degrees, the welding process starts with homoepitaxial nucleation of an initial Ag layer on (100) surface facets, considered to have an infinitely large radius of curvature. However, the strong driving force for this process due to the Gibbs-Thomson effect, requires the NW contact to occur through the corner of the pentagonal cross-section of the second NW providing a small radius of curvature. After the initial layer is formed, the welded zone continues to grow and extends out epitaxially to the neighboring twin segments.
Some results on the structure of constacyclic codes and new linear codes over GF(7) from quasi-twisted codes
Nuh Aydin, Nicholas Connolly, Markus Grassl
ADVANCES IN MATHEMATICS OF COMMUNICATIONS
11(1)
245-258
(2017)
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Journal
One of the most important and challenging problems in coding theory is to construct codes with good parameters. There are various methods to construct codes with the best possible parameters. A promising and fruitful approach has been to focus on the class of quasi-twisted (QT) codes which includes constacyclic codes as a special case. This class of codes is known to contain many codes with good parameters. Although constacyclic codes and QT codes have been the subject of numerous studies and computer searches over the last few decades, we have been able to discover a new fundamental result about the structure of constacyclic codes which was instrumental in our comprehensive search method for new QT codes over GF(7). We have been able to find 41 QT codes with better parameters than the previously best known linear codes. Furthermore, we derived a number of additional new codes via Construction X as well as standard constructions, such as shortening and puncturing.
Lempel-Ziv Complexity of Photonic Quasicrystals
Juan J. Monzon, Angel Felipe, Luis L. Sanchez-Soto
The properties of one-dimensional photonic quasicrystals ultimately rely on their nontrivial long-range order, a hallmark that can be quantified in many ways depending on the specific aspects to be studied. Here, we assess the quasicrystal structural features in terms of the Lempel-Ziv complexity. This is an easily calculable quantity that has proven to be useful for describing patterns in a variety of systems. One feature of great practical relevance is that it provides a reliable measure of how hard it is to create the structure. Using the generalized Fibonacci quasicrystals as our thread, we give analytical fitting formulas for the dependence of the optical response with the complexity.
Extracting the physical sector of quantum states
D. Mogilevtsev, Y. S. Teo, J. Rehacek, Z. Hradil, J. Tiedau, R. Kruse, G. Harder, C. Silberhorn, L. L. Sanchez-Soto
The physical nature of any quantum source guarantees the existence of an effective Hilbert space of finite dimension, the physical sector, in which its state is completely characterized with arbitrarily high accuracy. The extraction of this sector is essential for state tomography. We show that the physical sector of a state, defined in some pre-chosen basis, can be systematically retrieved with a procedure using only data collected from a set of commuting quantum measurement outcomes, with no other assumptions about the source. We demonstrate the versatility and efficiency of the physical-sector extraction by applying it to simulated and experimental data for quantum light sources, as well as quantum systems of finite dimensions.
Sascha Preu, Christian Mueller-Landau, Stefan Malzer, Gottfried H. Doehler, Hong Lu, Arthur C. Gossard, Daniel Segovia-Vargas, Alejandro Rivera-Lavado, Enrique L. Garcia-Munoz
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
65(7)
3474-3480
(2017)
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Journal
We have fiber-coupled an array of n-i-pn-i-p superlattice photomixers using a fiber array of same pitch of 145 mu m. We experimentally investigate the effect of the finite size of the implemented silicon lens on the interference between the array elements in the far field. We compare the results from a geometry optimized for a collimated terahertz (THz) beam to theory and simulations. Further, beam steering is demonstrated by controlling the optical phase of the individual photomixers. Due to broadband antennas attached to each array element, the array is frequency tunable. It is exemplarily characterized at 165 and 310 GHz. Such arrays can overcome power limitations of individual photomixers. In contrast to bulky individually packaged free space solutions, this array can be packaged to a compact terahertz source, limited in size only by the size of the silicon lens. The investigated 2 x 2 array features a spot diameter (full-width at half-maximum) of 12.1 mm at a distance of 19 cm at 310 GHz with a silicon lens of only 20-mm diameter.
Experimental detection of entanglement polytopes via local filters
Yuan-Yuan Zhao, Markus Grassl, Bei Zeng, Guo-Yong Xiang, Chao Zhang, Chuan-Feng Li, Guang-Can Guo
Quantum entanglement, resulting in correlations between subsystems that are stronger than any possible classical correlation, is one of the mysteries of quantum mechanics. Entanglement cannot be increased by any local operation, and for a sufficiently large many-body quantum system there exist infinitely many different entanglement classes, i. e., states that are not related by stochastic local operations and classical communications. On the other hand, the method of entanglement polytopes results in finitely many coarse-grained types of entanglement that can be detected by only measuring single-particle spectra. We find, however, that with high probability the local spectra lie in more than one polytope, hence providing only partial information about the entanglement type. To overcome this problem, we propose to additionally use so-called local filters, which are non-unitary local operations. We experimentally demonstrate the detection of entanglement polytopes in a four-qubit system. Using local filters we can distinguish the entanglement type of states with the same single particle spectra, but which belong to different polytopes.
Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures
George Sarau, Martin Heilmann, Muhammad Bashouti, Michael Latzel, Christian Tessarek, Silke Christiansen
doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of similar to 11 atom % without virtually inducing new structural defects in the initial, large-area, low defect, and transferred single-layer graphene. To shed light on this remarkable high-doping Iow-disorder relationship, a unique experimental strategy consisting of analyzing the changes in doping, strain) and defect density after each important step during :the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods On top of graphene, leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended toward integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.
Effect of stray fields on Rydberg states in hollow-core PCF probed by
higher-order modes
G. Epple, N. Y. Joly, T. G. Euser, P. St. J. Russell, R. Loew
The spectroscopy of atomic gases confined in hollow-core photonic crystal fiber (HC-PCF) provides optimal atom-light coupling beyond the diffraction limit, which is desirable for various applications such as sensing, referencing, and nonlinear optics. Recently, coherent spectroscopy was carried out on highly excited Rydberg states at room temperature in a gas-filled HC-PCF. The large polarizability of the Rydberg states made it possible to detect weak electric fields inside the fiber. In this Letter, we show that by combining highly excited Rydberg states with higher-order optical modes, we can gain insight into the distribution and underlying effects of these electric fields. Comparisons between experimental findings and simulations indicate that the fields are caused by the dipole moments of atoms adsorbed on the hollow-core wall. Knowing the origin of the electric fields is an important step towards suppressing them in future HC-PCF experiments. Furthermore, a better understanding of the influence of adatoms will be advantageous for optimizing electric-fieldsensitive experiments carried out in the vicinity of nearby surfaces. (C) 2017 Optical Society of America
Development of an optimal filter substrate for the identification of small microplastic particles in food by micro-Raman spectroscopy
Barbara E. Ossmann, George Sarau, Sebastian W. Schmitt, Heinrich Holtmannspoetter, Silke H. Christiansen, Wilhelm Dicke
ANALYTICAL AND BIOANALYTICAL CHEMISTRY
409(16)
4099-4109
(2017)
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Journal
When analysing microplastics in food, due to toxicological reasons it is important to achieve clear identification of particles down to a size of at least 1 mu m. One reliable, optical analytical technique allowing this is micro-Raman spectroscopy. After isolation of particles via filtration, analysis is typically performed directly on the filter surface. In order to obtain high qualitative Raman spectra, the material of the membrane filters should not show any interference in terms of background and Raman signals during spectrum acquisition. To facilitate the usage of automatic particle detection, membrane filters should also show specific optical properties. In this work, beside eight different, commercially available membrane filters, three newly designed metal-coated polycarbonate membrane filters were tested to fulfil these requirements. We found that aluminium-coated polycarbonate membrane filters had ideal characteristics as a substrate for micro-Raman spectroscopy. Its spectrum shows no or minimal interference with particle spectra, depending on the laser wavelength. Furthermore, automatic particle detection can be applied when analysing the filter surface under dark-field illumination. With this new membrane filter, analytics free of interference of microplastics down to a size of 1 mu m becomes possible. Thus, an important size class of these contaminants can now be visualized and spectrally identified.
Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light
J. R. Koehler, R. E. Noskov, A. A. Sukhorukov, D. Novoa, P. St. J. Russell
Coherent control of the resonant response in spatially extended optomechanical structures is complicated by the fact that the optical drive is affected by the backaction from the generated phonons. Here we report an approach to coherent control based on stimulated Raman-like scattering, in which the optical pressure can remain unaffected by the induced vibrations even in the regime of strong optomechanical interactions. We demonstrate experimentally coherent control of flexural vibrations simultaneously along the whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase between the components of a two-frequency pump signal, the beat frequency being chosen to match a flexural resonance. Furthermore, sequential switching of the relative phase at time intervals shorter than the lifetime of the vibrations reduces their amplitude to a constant value that is fully adjustable by tuning the phase modulation depth and switching rate. The results may trigger new developments in silicon photonics, since such coherent control uniquely decouples the amplitude of optomechanical oscillations from power-dependent thermal effects and nonlinear optical loss.
Light-matter interactions in multi-element resonators
Claudiu Genes, Aurelien Dantan
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
50(10)
105502
(2017)
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Journal
We investigate light-matter interactions in multi-element optical resonators and provide a roadmap for the identification of structural resonances and the description of the interaction of single extended cavity modes with quantum emitters or mechanical resonators. Using a first principle approach based on the transfer matrix formalism we analyze, both numerically and analytically, the static and dynamical properties of three-and four-mirror cavities. We investigate in particular conditions under which the confinement of the field in specific subcavities allows for enhanced light-matter interactions in the context of cavity quantum electrodynamics and cavity optomechanics.
Levitated Plasmonic Nanoantennas in an Aqueous Environment
Yazgan Tuna, Ji Tae Kim, Hsuan-Wei Liu, Vahid Sandoghdar
We report on the manipulation of a plasmonic nanoantenna in an aqueous solution using an electrostatic trap created between a glass nanopipette and a substrate. By scanning a trapped gold nanosphere in the near field of a single colloidal quantum dot embedded under the substrate surface, we demonstrate about 8-fold fluorescence enhancement over a lateral full width at half maximum of about 45 nm. We analyze our results with the predictions of numerical electromagnetic simulations under consideration of the electrostatic free energy in the trap. Our approach could find applications in a number of experiments, where plasmonic effects are employed at liquid solid interfaces.
Core-Shell Plasmonic Nanohelices
Dolfine Kosters, Anouk de Hoogh, Hans Zeijlemaker, Hakki Acar, Nir Rotenberg, L. Kuipers
We introduce core-shell plasmonic nanohelices, highly tunable structures that have a different response in the visible for circularly polarized light of opposite handedness. The glass core of the helices is fabricated using electron beam induced deposition and the pure gold shell is subsequently sputter coated. Optical measurements allow us to explore the chiral nature of the nanohelices, where differences in the response to circularly polarized light of opposite handedness result in a dissymmetry factor of 0.86, more than twice of what has been previously reported. Both experiments and subsequent numerical simulations demonstrate the extreme tunability of the core-shell structures, where nanometer changes to the geometry can lead to drastic changes of the optical responses. This tunability, combined with the large differential transmission, make core-shell plasmonic nanohelices a powerful nanophotonic tool for, for example, (bio)sensing applications.
Nonlinear-Photonics Devices on the Basis of the Coherent Interaction of Optical Radiation with Resonant Media (a Review)
R. M. Arkhipov, M. V. Arkhipov, A. V. Pakhomov, I. Babushkin, N. N. Rosanov
OPTICS AND SPECTROSCOPY
122(6)
949-954
(2017)
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Journal
We have examined examples of nonlinear-photonics devices that are based on the coherent interaction of light with matter. Such interaction takes place if the duration of a light pulse is shorter than the relaxation times T-1 and T-2 in a resonant medium and if the strength of the light field is so high that Rabi oscillations arise. Theoretical analysis shows that these systems have a number of advantages compared to similar devices that operate under incoherent interaction conditions of light with matter.
Continuously wavelength-tunable high harmonic generation via soliton dynamics
Francesco Tani, Michael H. Frosz, John C. Travers, Philip St. J. Russell
We report the generation of high harmonics in a gas jet pumped by pulses self-compressed in a He-filled hollow-core photonic crystal fiber through the soliton effect. The gas jet is placed directly at the fiber output. As the energy increases, the ionization-induced soliton blueshift is transferred to the high harmonics, leading to emission bands that are continuously tunable from 17 to 45 eV. (C) 2017 Optical Society of America
Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking
Carlos Navarrete-Benlloch, Giuseppe Patera, Germán J. de Valcarcel
Physical Review A
96(4)
043801
(2017)
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Journal
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PDF
Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities driven by mode-locked lasers, and containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. SPOPOs have received a lot of attention lately because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging and interesting regime where spontaneous symmetry breaking confers strong nonclassical properties to the emitted light, which has eluded experimental observation so far. Apart from opening the possibility of studying experimentally this elusive regime of dissipative phase transitions, our predictions will have a practical impact, since we show that spontaneous symmetry breaking provides a specific spatiotemporal mode with large quadrature squeezing for any value of the system parameters, turning SPOPOs into robust sources of highly nonclassical light above threshold.
Broadband high-resolution multi-species CARS in gas-filled hollow-core photonic crystal fiber
Barbara M. Trabold, Robert J. R. Hupfer, Amir Abdolvand, Philip St. J. Russell
We report the use of coherent anti-Stokes Raman spectros-copy (CARS) in gas-filled hollow-core photonic crystal fiber (HC-PCF) for trace gas detection. The long optical path-lengths yield a 60 dB increase in the signal level compared with free-space arrangements. This enables a relatively weak supercontinuum (SC) to be used as Stokes seed, along with a ns pump pulse, paving the way for broadband (> 4000 cm(-1)) single-shot CARS with an unprecedented resolution of similar to 100 MHz. A kagome-style HC-PCF provides broadband guidance, and, by operating close to the pressure-tunable zero dispersion wavelength, we can ensure simultaneous phase-matching of all gas species. We demonstrate simultaneous measurement of the concentrations of multiple trace gases in a gas sample introduced into the core of the HC-PCF. (C) 2017 Optical Society of America
Cavity-Enhanced Transport of Charge
David Hagenmueller, Johannes Schachenmayer, Stefan Schutz, Claudiu Genes, Guido Pupillo
We theoretically investigate charge transport through electronic bands of a mesoscopic one-dimensional system, where interband transitions are coupled to a confined cavity mode, initially prepared close to its vacuum. This coupling leads to light-matter hybridization where the dressed fermionic bands interact via absorption and emission of dressed cavity photons. Using a self-consistent nonequilibrium Green's function method, we compute electronic transmissions and cavity photon spectra and demonstrate how light-matter coupling can lead to an enhancement of charge conductivity in the steady state. We find that depending on cavity loss rate, electronic bandwidth, and coupling strength, the dynamics involves either an individual or a collective response of Bloch states, and we explain how this affects the current enhancement. We show that the charge conductivity enhancement can reach orders of magnitudes under experimentally relevant conditions.
Effect of ammonification temperature on the formation of coaxial GaN/Ga2O3 nanowires
Mukesh Kumar, George Sarau, Martin Heilmann, Silke Christiansen, Vikram Kumar, R. Singh
JOURNAL OF PHYSICS D-APPLIED PHYSICS
50(3)
035302
(2017)
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Journal
The effect of ammonification temperature on the formation of coaxial GaN/Ga2O3 nanowires from beta-Ga2O3 nanowires is reported in this work. High quality wurtzite GaN material showing a single c-plane phase is achieved from beta-Ga2O3 nanowires having monoclinic crystal structure at a high ammonification temperature of 1050 degrees C. Lower ammonification temperatures such as 900 degrees C are also adequate for achieving coaxial GaN/Ga2O3 nanowire heterostructures, and the degree of GaN phase can be adjusted by varying the ammonification temperature. The crystalline quality of GaN/Ga2O3 nanowires improves with increasing the ammonification temperature. Resonant Raman spectra of GaN/Ga2O3 nanowires show Raman progression through multiple longitudinal-optical-phonon modes with overtones of up to second order. The development and improvement of the emission peak toward the near band edge of GaN at different ammonification temperatures were investigated using cathodoluminescence and photoluminescence characterization.
Free-space propagation of high-dimensional structured optical fields in
an urban environment
Martin P. J. Lavery, Christian Peuntinger, Kevin Guenthner, Peter Banzer, Dominique Elser, Robert W. Boyd, Miles J. Padgett, Christoph Marquardt, Gerd Leuchs
Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantum-state tomography. We present experimental data for the modal degradation in a real urban environment and draw a comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in an urban environment.
Small slot waveguide rings for on-chip quantum optical circuits
Nir Rotenberg, Pierre Tuerschmann, Harald R. Haakh, Diego-Martin Cano, Stephan Goetzinger, Vahid Sandoghdar
Nanophotonic interfaces between single emitters and light promise to enable new quantum optical technologies. Here, we use a combination of finite element simulations and analytic quantum theory to investigate the interaction of various quantum emitters with slot-waveguide rings. We predict that for rings with radii as small as 1.44 mu m, with a Q-factor of 27,900, near-unity emitter-waveguide coupling efficiencies and emission enhancements on the order of 1300 can be achieved. By tuning the ring geometry or introducing losses, we show that realistic emitter-ring systems can be made to be either weakly or strongly coupled, so that we can observe Rabi oscillations in the decay dynamics even for micron-sized rings. Moreover, we demonstrate that slot waveguide rings can be used to directionally couple emission, again with near-unity efficiency. Our results pave the way for integrated solid-state quantum circuits involving various emitters. (C) 2017 Optical Society of America
Optimally cloned binary coherent states
C. R. Mueller, G. Leuchs, Ch. Marquardt, U. L. Andersen
Binary coherent state alphabets can be represented in a two-dimensional Hilbert space. We capitalize this formal connection between the otherwise distinct domains of qubits and continuous variable states to map binary phase-shift keyed coherent states onto the Bloch sphere and to derive their quantum-optimal clones. We analyze the Wigner function and the cumulants of the clones, and we conclude that optimal cloning of binary coherent states requires a nonlinearity above second order. We propose several practical and near-optimal cloning schemes and compare their cloning fidelity to the optimal cloner.
Production of Isolated Giant Unilamellar Vesicles under High Salt
Concentrations
Hannah Stein, Susann Spindler, Navid Bonakdar, Chun Wang, Vahid Sandoghdar
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of mu m in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
Temporal and spectral properties of quantum light
B. Stiller, U. Seyfarth, G. Leuchs, C. Fabre, V. Sandoghdar, N. Treps, L.F. Cugliandolo
Quantum Optics and Nanophotonics
169-227
(2017)
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Book Chapter
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PDF
New self-dual additive F_4-codes constructed from circulant graphs
In order to construct quantum [[n, 0, d]] codes for (n, d) = (56, 15), (57, 15), (58, 16), (63, 16), (67, 17), (70, 18), (71, 18), (79, 19), (83, 20), (87, 20), (89, 21), (95, 20), we construct self-dual additive F-4-codes of length n and minimum weight d from circulant graphs. The quantum codes with these parameters are constructed for the first time. (C) 2016 Elsevier B.V. All rights reserved.
Free-space quantum links under diverse weather conditions
D. Vasylyev, A. A. Semenov, W. Vogel, K. Guenthner, A. Thurn, O. Bayraktar, Ch. Marquardt
Free-space optical communication links are promising channels for establishing secure quantum communication. Here we study the transmission of nonclassical light through a turbulent atmospheric link under diverse weather conditions, including rain or haze. To include these effects, the theory of light transmission through atmospheric links in the elliptic-beam approximation presented by Vasylyev et al. [D. Vasylyev et al., Phys. Rev. Lett. 117, 090501 (2016)] is further generalized. It is demonstrated, with good agreement between theory and experiment, that low-intensity rain merely contributes additional deterministic losses, whereas haze also introduces additional beam deformations of the transmitted light. Based on these results, we study theoretically the transmission of quadrature squeezing and Gaussian entanglement under these weather conditions.
High-dimensional intracity quantum cryptography with structured photons
Alicia Sit, Frederic Bouchard, Robert Fickler, Jeremie Gagnon-Bischoff, Hugo Larocque, Khabat Heshami, Dominique Elser, Christian Peuntinger, Kevin Guenthner, et al.
Quantum key distribution (QKD) promises information-theoretically secure communication and is already on the verge of commercialization. The next step will be to implement high-dimensional protocols in order to improve noise resistance and increase the data rate. Hitherto, no experimental verification of high-dimensional QKD in the singlephoton regime has been conducted outside of the laboratory. Here, we report the realization of such a single-photon QKD system in a turbulent free-space link of 0.3 km over the city of Ottawa, taking advantage of both the spin and orbital angular momentum photonic degrees of freedom. This combination of optical angular momenta allows us to create a 4-dimensional quantum state; wherein, using a high-dimensional BB84 protocol, a quantum bit error rate of 11% was attained with a corresponding secret key rate of 0.65 bits per sifted photon. In comparison, an error rate of 5% with a secret key rate of 0.43 bits per sifted photon is achieved for the case of 2-dimensional structured photons. We thus demonstrate that, even through moderate turbulence without active wavefront correction, high-dimensional photon states are advantageous for securely transmitting more information. This opens the way for intracity high-dimensional quantum communications under realistic conditions. (C) 2017 Optical Society of America
Quantum-limited measurements of optical signals from a geostationary
satellite
Kevin Guenthner, Imran Khan, Dominique Elser, Birgit Stiller, Oemer Bayraktar, Christian R. Mueller, Karen Saucke, Daniel Troendle, Frank Heine, et al.
The measurement of quantum signals that travel through long distances is fundamentally and technologically interesting. We present quantum-limited coherent measurements of optical signals that are sent from a satellite in geostationary Earth orbit to an optical ground station. We bound the excess noise that the quantum states could have acquired after having propagated 38,600 km through Earth's gravitational potential, as well as its turbulent atmosphere. Our results indicate that quantum communication is feasible, in principle, in such a scenario, highlighting the possibility of a global quantum key distribution network for secure communication. (C) 2017 Optical Society of America
Towards next-generation label-free biosensors: recent advances in whispering gallery mode sensors
Whispering gallery mode biosensors have been widely exploited over the past decade to study molecular interactions by virtue of their high sensitivity and applicability in real-time kinetic analysis without the requirement to label. There have been immense research efforts made for advancing the instrumentation as well as the design of detection assays, with the common goal of progressing towards real-world sensing applications. We therefore review a set of recent developments made in this field and discuss the requirements that whispering gallery mode label-free sensors need to fulfill for making a real world impact outside of the laboratory. These requirements are directly related to the challenges that these sensors face, and the methods proposed to overcome them are discussed. Moving forward, we provide the future prospects and the potential impact of this technology.
On diagnostics of media using extremely short terahertz radiation pulses
N. N. Rosanov, M. V. Arkhipov, R. M. Arkhipov, A. V. Pakhomov, I. V. Babushkin
OPTICS AND SPECTROSCOPY
123(1)
100-104
(2017)
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Journal
The possibility of diagnosing the linear and nonlinear electrodynamic susceptibilities of media by examining the time profiles of extremely short terahertz radiation pulses (using pulsed terahertz spectroscopy methods) that are incident on a thin layer of a medium under study, are reflected from the layer, and are transmitted through it is shown theoretically. In the general case, the linear and nonlinear susceptibilities of different orders can be found by solving linear integral equations. Diagnostics is considerably simplified in the case of an isolated resonance of a medium with homogeneous spectral broadening, which is modeled by the response of an anharmonic oscillator.
A Single-Emitter Gain Medium for Bright Coherent Radiation from a Plasmonic Nanoresonator
Pu Zhang, Igor Protsenko, Vahid Sandoghdar, Xue-Wen Chen
We propose and demonstrate theoretically bright coherent radiation from a plasmonic nanoresonator powered by a single three-level quantum emitter. By introducing a dual-pump scheme in a Raman configuration for the three-level system, we overcome the fast decay of nanoplasmons and achieve macroscopic accumulation of nanoplasmons on the plasmonic nanoresonator for stimulated emission. We utilize the optical antenna effect for efficient radiation of the nanoplasmons and predict photon emission rates of 100 THz with up to 10 ps duration pulses and GHz repetition rates with the consideration of possible heating issue. We show that the ultrafast nature of the nanoscopic coherent source allows for operation with solid-state emitters at room temperature in the presence of fast dephasing. We provide physical interpretations of the results and discuss their realization and implications for ultracompact integration of optoelectronics.
Orbital angular momentum modes of high-gain parametric down-conversion
Lina Beltran, Gaetano Frascella, Angela M. Perez, Robert Fickler, Polina R. Sharapova, Mathieu Manceau, Olga V. Tikhonova, Robert W. Boyd, Gerd Leuchs, et al.
Light beams with orbital angular momentum (OAM) are convenient carriers of quantum information. They can. also be. used for imparting rotational motion to particles and providing. high resolution in imaging. Due to the conservation of OAM in parametric down-conversion (PDC), signal and idler photons generated at low gain have perfectly anti-correlated OAM values. It is interesting to study the OAM properties of high-gain PDC, where the same OAM modes can be populated with large, but correlated, numbers of photons. Here we investigate the OAM spectrum of high-gain PDC and show that the OAM mode content can be controlled by varying the pump power and the configuration of the source. In our experiment, we use a source consisting of two nonlinear crystals separated by an air gap. We discuss the OAM properties of PDC radiation emitted by this source and suggest possible modifications.
Mid-infrared dispersive wave generation in gas-filled photonic crystal fibre by transient ionization-driven changes in dispersion
F. Koettig, D. Novoa, F. Tani, M. C. Guenendi, M. Cassataro, J. C. Travers, P. St. J. Russell
Gas-filled hollow-core photonic crystal fibre is being used to generate ever wider super-continuum spectra, in particular via dispersive wave emission in the deep and vacuum ultraviolet, with a multitude of applications. Dispersive waves are the result of nonlinear transfer of energy from a self-compressed soliton, a process that relies crucially on phase-matching. It was recently predicted that, in the strong-field regime, the additional transient anomalous dispersion introduced by gas ionization would allow phase-matched dispersive wave generation in the mid-infrared-something that is forbidden in the absence of free electrons. Here we report the experimental observation of such mid-infrared dispersive waves, embedded in a 4.7-octave-wide supercontinuum that uniquely reaches simultaneously to the vacuum ultraviolet, with up to 1.7W of total average power.
Refractometry-based air pressure sensing using glass microspheres as high-Q whispering-gallery mode microresonators
Arturo Bianchetti, Alejandro Federico, Serge Vincent, Sivaraman Subramanian, Frank Vollmer
In this work a refractometric air pressure sensing platform timed on spherical whispering-gallery mode microresonators is presented and analyzed. The sensitivity of this sensing approach is characterized by measuring the whispering-gallery mode spectral shifts caused by a change of air refractive index produced by dynamic sinusoidal pressure variations that lie between extremes of +/- 1.81 kPa. A theoretical frame of work is developed to characterize the refractometric air pressure sensing platform by using the Ciddor equation for the refractive index of air, and a comparison is made against experimental results for the purpose of performance evaluation.
Optimal measurements for resolution beyond the Rayleigh limit
J. Rehacek, M. Paur, B. Stoklasa, Z. Hradil, L. L. Sanchez-Soto
We establish the conditions to attain the ultimate resolution predicted by quantum estimation theory for the case of two incoherent point sources using a linear imaging system. The solution is closely related to the spatial symmetries of the detection scheme. In particular, for real symmetric point spread functions, any complete set of projections with definite parity achieves the goal. (C) 2017 Optical Society of America
PHz-Wide Spectral Interference Through Coherent Plasma-Induced Fission of Higher-Order Solitons
F. Koettig, F. Tani, J. C. Travers, P. St. J. Russell
We identify a novel regime of soliton-plasma interactions in which high-intensity ultrashort pulses of intermediate soliton order undergo coherent plasma-induced fission. Experimental results obtained in gas-filled hollow-core photonic crystal fiber are supported by rigorous numerical simulations. In the anomalous dispersion regime, the cumulative blueshift of higher-order input solitons with ionizing intensities results in pulse splitting before the ultimate self-compression point, leading to the generation of robust pulse pairs with PHz bandwidths. The novel dynamics closes the gap between plasma-induced adiabatic soliton compression and modulational instability.
Optical gating and streaking of free electrons with sub-optical cycle
precision
M. Kozak, J. McNeur, K. J. Leedle, H. Deng, N. Schoenenberger, A. Ruehl, I. Hartl, J. S. Harris, R. L. Byer, et al.
The temporal resolution of ultrafast electron diffraction and microscopy experiments is currently limited by the available experimental techniques for the generation and characterization of electron bunches with single femtosecond or attosecond durations. Here, we present proof of principle experiments of an optical gating concept for free electrons via direct time-domain visualization of the sub-optical cycle energy and transverse momentum structure imprinted on the electron beam. We demonstrate a temporal resolution of 1.2 +/- 0.3 fs. The scheme is based on the synchronous interaction between electrons and the near-field mode of a dielectric nano-grating excited by a femtosecond laser pulse with an optical period duration of 6.5 fs. The sub-optical cycle resolution demonstrated here is promising for use in laser-driven streak cameras for attosecond temporal characterization of bunched particle beams as well as time-resolved experiments with free-electron beams.
All-optical control of unipolar pulse generation in a resonant medium with nonlinear field coupling
A. V. Pakhomov, R. M. Arkhipov, I. V. Babushkin, M. V. Arkhipov, Yu. A. Tolmachev, N. N. Rosanov
We study the optical response of a resonant medium possessing nonlinear coupling to an external field driven by a few-cycle pump pulse sequence. We demonstrate the possibility of directly producing unipolar half-cycle pulses from the medium possessing an arbitrary nonlinearity, by choosing the proper pulse-to-pulse distance of the pump pulses in the sequence. We examine various ways of shaping the medium response using different geometrical configurations of nonlinear oscillators and different wavefront shapes for the excitation pulse sequence. Our approach defines a general framework to produce unipolar pulses of controllable form.
Broadband, Lensless, and Optomechanically Stabilized Coupling into Microfluidic Hollow-Core Photonic Crystal Fiber Using Glass Nanospike
Richard Zeltner, Shangran Xie, Riccardo Pennetta, Philip St J. Russell
We report a novel technique for launching broadband laser light into liquid-filled hollow-core photonic crystal fiber (HC-PCF). It uniquely offers self alignment and self-stabilization via optomechanical trapping of a,fused silica nanospike, fabricated by thermally tapering and chemically etching a single mode fiber into a tip diameter of 350 nm. We show that a trapping laser, deliirering similar to 300 mW at 1064 nm, can be used to optically align and stably maintain the iianospike at the core center. Once this is done, a weak broadband supercontinuum signal (similar to 575-1064 nm) can be efficiently and close to achromatically launched in the HC-PCF. The system is robust against liquid-flow in either direction inside the HC-PCF, and the Fresnel back-reflections are reduced to negligible levels compared to free-space launching or butt-coupling. The results are of potential relevance for any application where the efficient delivery of broadband light into liquid-core waveguides is desired.
Quantum communication with coherent states of light
Imran Khan, Dominique Elser, Thomas Dirmeier, Christoph Marquardt, Gerd Leuchs
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL
AND ENGINEERING SCIENCES
375(2099)
20160235
(2017)
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Journal
Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics ( information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links.
This article is part of the themed issue 'Quantum technology for the 21st century'.
Enhanced Control of Transient Raman Scattering Using Buffered Hydrogen in Hollow-Core Photonic Crystal Fibers
P. Hosseini, D. Novoa, A. Abdolvand, P. St. J. Russell
Many reports on stimulated Raman scattering in mixtures of Raman-active and noble gases indicate that the addition of a dispersive buffer gas increases the phase mismatch to higher-order Stokes and anti-Stokes sidebands, resulting in a preferential conversion to the first few Stokes lines, accompanied by a significant reduction in the Raman gain due to collisions with gas molecules. Here we report that, provided the dispersion can be precisely controlled, the effective Raman gain in a gas-filled hollow-core photonic crystal fiber can actually be significantly enhanced when a buffer gas is added. This counterintuitive behavior occurs when the nonlinear coupling between the interacting fields is strong and can result in a performance similar to that of a pure Raman-active gas, but at a much lower total gas pressure, allowing competing effects such as Raman backscattering to be suppressed. We report high modal purity in all the emitted sidebands, along with anti-Stokes conversion efficiencies as high as 5% in the visible and 2% in the ultraviolet. This new class of gas-based waveguide device, which allows the nonlinear optical response to be beneficially pressure-tuned by the addition of buffer gases, may find important applications in laser science and spectroscopy.
Rapid screening of photoactivatable metallodrugs: photonic crystal fibre
microflow reactor coupled to ESI mass spectrometry
Ruth J. McQuitty, Sarah Unterkofler, Tijmen G. Euser, Philip St J. Russell, Peter J. Sadler
We explore the efficacy of a hyphenated photonic crystal fibre microflow reactor-high-resolution mass spectrometer system as a method for screening the activity of potential new photoactivatable drugs. The use of light to activate drugs is an area of current development as it offers the possibility of reduced side effects due to improved spatial and temporal targeting and novel mechanisms of anticancer activity. The di-nuclear ruthenium complex [{(eta(6)-indan) RuCl}(2)(mu-2,3-dpp)](PF6)(2), previously studied by Magennis et al. (Inorg. Chem., 2007, 46, 5059) is used as a model drug to compare the system to standard irradiation techniques. The photodecomposition pathways using blue light radiation are the same for PCF and conventional cuvette methods. Reactions in the presence of small biomolecules 50-guanosine monophosphate (5'-GMP), 5'-adenosine monophosphate (5'-AMP), L-cysteine (L-Cys) and glutathione (gamma-L-glutamyl-L-cysteinyl-glycine, GSH) were studied. The complex was found to bind to nucleobases in the dark and this binding increased upon irradiation with 488 nm light, forming the adducts [(eta(6)-indan) Ru2(mu-2,3-dpp) + 5'-GMP](2+) and [(eta(6)-indan) Ru + (5'-AMP)]+. These findings are consistent with studies using conventional methods. The dinuclear complex also binds strongly to GSH after irradiation, a possible explanation for its lack of potency in cell line testing. The use of the PCF-MS system dramatically reduced the sample volume required and reduced the irradiation time by four orders of magnitude from 14 hours to 12 seconds. However, the reduced sample volume also results in a reduced MS signal intensity. The dead time of the combined system is 15 min, limited by the intrinsic dead volume of the HR-MS.
Discrete phase-space structures and Wigner functions for N qubits
C. Munoz, A. B. Klimov, L. Sanchez-Soto
QUANTUM INFORMATION PROCESSING
16(6)
UNSP 158
(2017)
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Journal
We further elaborate on a phase-space picture for a system of N qubits and explore the structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves satisfying certain additional properties and different entanglement properties. We discuss the construction of discrete covariant Wigner functions for these bundles and provide several illuminating examples.
acoustic sensor, with the ability to detect and retrieve actual temporal waveforms of multiple vibration events that occur simultaneously at different positions along the fiber. The system is realized via a dual-pulse phase-sensitive optical time-domain reflectometry, and the actual waveform is retrieved by heterodyne phase demodulation. Experimental results show that the system has a background noise level as low as 8.91 x 10(-4) rad/root Hz with a demodulation signal-to-noise ratio of 49.17 dB at 1 kHz, and can achieve a dynamic range of similar to 60 dB at 1 kHz (0.1 to 104 rad) for phase demodulation, as well as a detection frequency range from 20 Hz to 25 kHz. (C) 2017 Optical Society of America
Optical alignment of oval graphene flakes
E. Mobini, A. Rahimzadegan, R. Alaee, C. Rockstuhl
Patterned graphene, as an atomically thin layer, supports localized surface plasmon polaritons at mid-infrared or far-infrared frequencies. This provides a pronounced optical force/torque in addition to large optical cross sections and will make it an ideal candidate for optical manipulation. Here, we study the optical force and torque exerted by a linearly polarized plane wave on circular and oval graphene flakes (single layers of graphene). While the torque vanishes for circular flakes, the finite torque allows rotating and orienting oval flakes relative to the electric field polarization. Depending on the wavelength, the alignment is either parallel or perpendicular to the electric field vector. In our contribution, we rely on a full-wave numerical simulation and also on an analytical model that treats the graphene flakes in a dipole approximation. The presented results reveal a good level of control on the spatial alignment of graphene flakes subjected to far-infrared illumination. (C) 2017 Optical Society of America
Radiation of a resonant medium excited by few-cycle optical pulses at
superluminal velocity
R. M. Arkhipov, A. V. Pakhomov, M. V. Arkhipov, I. Babushkin, Yu A. Tolmachev, N. N. Rosanov
Recent progress in generation of optical pulses of durations comparable to one optical cycle has presented great opportunities for studies of the fundamental processes in matter as well as time-resolved spectroscopy of ultrafast processes in nonlinear media. It opened up a new area of research in modern ultrafast nonlinear optics and led to appearance of the attosecond science. In parallel, a new research area related to emission from resonant media excited by superluminally propagating ultrashort bursts of electromagnetic radiation has been actively developed over the last few years. In this paper, we review our recent results on theoretical analysis of the Cherenkov-type radiation of a resonant medium excited by few-cycle optical pulses propagating at superluminal velocity. This situation can be realized when an electromagnetic pulse with a plane wavefront incidents on a straight string of resonant atoms or a spot of light rotates at very large angular frequency and excites a distant circular string of resonant dipoles. Theoretical analysis revealed some unusual and remarkable features of the Cherenkov radiation generated in this case. This radiation arises in a transient regime which leads to the occurrence of new frequencies in the radiation spectrum. Analysis of the characteristics of this radiation can be used for the study of the resonant structure properties. In addition, a nonlinear resonant medium excited at superluminal velocity can emit unipolar optical pulses, which can be important in ultrafast control of wave-packet dynamics of matter. Specifics of the few-cycle pulse-driven optical response of a resonant medium composed of linear and nonlinear oscillators is discussed.
Experimental demonstration of a predictable single photon source with
variable photon flux
Aigar Vaigu, Geiland Porrovecchio, Xiao-Liu Chu, Sarah Lindner, Marek Smid, Albert Manninen, Christoph Becher, Vahid Sandoghdar, Stephan Gotzinger, et al.
We present a predictable single-photon source (SPS) based on a silicon vacancy centre in nanodiamond which is optically excited by a pulsed laser. At an excitation rate of 70 MHz the source delivers a photon flux large enough to be measured by a low optical flux detector (LOFD). The directly measured photon flux constitutes an absolute reference. By changing the repetition rate of the pulsed laser, we are able to change the photon flux of our SPS in a controllable way which in turn can act as a reference. The advantage of our method is that it does not require precise knowledge of the source efficiency, but the source is calibrated by the LOFD and can be used for detector responsivity characterizations at the few-photon level.
Using the focal phase to control attosecond processes
Dominik Hoff, Michael Krueger, Lothar Maisenbacher, Gerhard G. Paulus, Peter Hommelhoff, A. M. Sayler
The spatial evolution of the electric field of focused broadband light is crucial for many emerging attosecond technologies. Here the effects of the input beam parameters on the evolution of few-cycle laser pulses in the focus are discussed. Specifically, we detail how the frequency-dependent input beam geometry, chirp and chromatic aberration can affect the spatial dependence of the carrier-envelope phase (CEP), central frequency and pulse duration in the focus. These effects are confirmed by a direct, three-dimensional measurement of the CEP-evolution in the focus of a typical few-cycle pulse laser using electron rescattering at metal nanotips in combination with a CEP-metre. Moreover, we demonstrate a simple measurement technique to estimate the focal CEP evolution by input-beam parameters. These parameters can be used in novel ways in order to control attosecond dynamics and tailor highly nonlinear light-matter interactions.
Improving the phase super-sensitivity of squeezing-assisted
interferometers by squeeze factor unbalancing
The sensitivity properties of an SU(1,1) interferometer made of two cascaded parametric amplifiers, as well as of an ordinary SU(2) interferometer preceded by a squeezer and followed by an anti-squeezer, are theoretically investigated. Several possible experimental configurations are considered, such as the absence or presence of a seed beam, direct or homodyne detection scheme. In all cases we formulate the optimal conditions to achieve phase super-sensitivity, meaning a sensitivity overcoming the shotnoise limit. Weshow that for a given gain of the first parametric amplifier, unbalancing the interferometer by increasing the gain of the second amplifier improves the interferometer properties. In particular, a broader super-sensitivity phase range and a better overall sensitivity can be achieved by gain unbalancing.
Polarization and phase-shifting interferometry for arbitrary, locally
varying polarization states
Sergej Rothau, Christine Kellermann, Simon Mayer, Klaus Mantel, Norbert Lindlein
This publication presents what we believe is a novel interferometric method for the simultaneous measurement of the phase and state of polarization of a light wave with arbitrary polarization; in particular, it can be varying elliptical. The measurement strategy is based on variations of the reference wave, concerning phase and polarization and processing the interference patterns so obtained. With this method, which is very similar to classical phase-shifting interferometry, the general analysis of spatially variant states of polarization and their phase fronts can be done in one measurement cycle. Furthermore, the analysis of different optical elements regarding the impact on the polarization and phase of the incoming light can be realized. After the theoretical description of the method and the mathematical discussion of different algorithms, the realized measurement setup is presented. Afterward, the accuracy of the method is discussed.(C) 2017 Optical Society of America
The Formation of Calcified Nanospherites during Micropetrosis Represents a Unique Mineralization Mechanism in Aged Human Bone
Petar Milovanovic, Elizabeth A. Zimmermann, Annika vom Scheidt, Bjoern Hoffmann, George Sarau, Timur Yorgan, Michaela Schweizer, Michael Amling, Silke Christiansen, et al.
Osteocytes-the central regulators of bone remodeling-are enclosed in a network of microcavities (lacunae) and nanocanals (canaliculi) pervading the mineralized bone. In a hitherto obscure process related to aging and disease, local plugs in the lacuno-canalicular network disrupt cellular communication and impede bone homeostasis. By utilizing a suite of high-resolution imaging and physics-based techniques, it is shown here that the local plugs develop by accumulation and fusion of calcified nanospherites in lacunae and canaliculi (micropetrosis). Two distinctive nanospherites phenotypes are found to originate from different osteocytic elements. A substantial deviation in the spherites' composition in comparison to mineralized bone further suggests a mineralization process unlike regular bone mineralization. Clearly, mineralization of osteocyte lacunae qualifies as a strong marker for degrading bone material quality in skeletal aging. The understanding of micropetrosis may guide future therapeutics toward preserving osteocyte viability to maintain mechanical competence and fracture resistance of bone in elderly individuals.
Higher-order mode suppression in twisted single-ring hollow-core photonic crystal fibers
N. N. Edavalath, M. C. Guenendi, R. Beravat, G. K. L. Wong, M. H. Frosz, J. -M. Menard, P. St. J. Russell
A hollow-core single-ring photonic crystal fiber (SR-PCF) consists of a ring of capillaries arranged around a central hollow core. Spinning the preform during drawing introduces a continuous helical twist, offering a novel means of controlling the modal properties of hollow-core SR-PCF. For example, twisting geometrically increases the effective axial propagation constant of the LP01-like modes of the capillaries, providing a means of optimizing the suppression of HOMs, which occurs when the LP11-like core mode phase-matches to the LP01-like modes of the surrounding capillaries. (In a straight fiber, optimum suppression occurs for a capillary-to-core diameter ratio d/D = 0.682.) Twisting also introduces circular birefringence (to be studied in a future Letter) and has a remarkable effect on the transverse intensity profiles of the higher-order core modes, forcing the two-lobed LP11-like mode in the untwisted fiber to become three-fold symmetric in the twisted case. These phenomena are explored by means of extensive numerical modeling, an analytical model, and a series of experiments. Prism-assisted side-coupling is used to measure the losses, refractive indices, and near-field patterns of individual fiber modes in both the straight and twisted cases. (C) 2017 Optical Society of America
Potential of PEDOT: PSS as a hole selective front contact for silicon
heterojunction solar cells
Sara Jaeckle, Martin Liebhaber, Clemens Gersmann, Mathias Mews, Klaus Jaeger, Silke Christiansen, Klaus Lips
We show that the highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) can successfully be applied as a hole selective front contact in silicon heterojunction (SHJ) solar cells. In combination with a superior electron selective heterojunction back contact based on amorphous silicon (a-Si), mono-crystalline n-type silicon (c-Si) solar cells reach power conversion efficiencies up to 14.8% and high open-circuit voltages exceeding 660 mV. Since in the PEDOT: PSS/cSi/ a-Si solar cell the inferior hybrid junction is determining the electrical device performance we are capable of assessing the recombination velocity (v(I)) at the PEDOT: PSS/c-Si interface. An estimated v(I) of similar to 400 cm/s demonstrates, that while PEDOT: PSS shows an excellent selectivity on n-type c-Si, the passivation quality provided by the formation of a native oxide at the c-Si surface restricts the performance of the hybrid junction. Furthermore, by comparing the measured external quantum efficiency with optical simulations, we quantify the losses due to parasitic absorption of PEDOT: PSS and reflection of the device layer stack. By pointing out ways to better passivate the hybrid interface and to increase the photocurrent we discuss the full potential of PEDOT: PSS as a front contact in SHJ solar cells.
Experimental demonstration of negative-valued polarization
quasiprobability distribution
Polarization quasiprobability distribution defined in the Stokes space shares many important properties with the Wigner function for position and momentum. Most notably, they both give correct one-dimensional marginal probability distributions and therefore represent the natural choice for the probability distributions in classical hidden-variable models. In this context, negativity of the Wigner function is considered as proof of nonclassicality for a quantum state. On the contrary, the polarization quasiprobability distribution demonstrates negativity for all quantum states. This feature comes from the discrete nature of Stokes variables; however, it was not observed in previous experiments, because they were performed with photon-number averaging detectors. Here we reconstruct the polarization quasiprobability distribution of a coherent state with photon-number resolving detectors, which allows us to directly observe for the first time its negativity. Furthermore we derive a theoretical polarization quasiprobability distribution for any linearly polarized quantum state.
Helically twisted photonic crystal fibres
P. St. J. Russell, Ramin Beravat, G. K. L. Wong
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL
AND ENGINEERING SCIENCES
375(2087)
20150440
(2017)
|
Journal
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left-and rightspinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic 'space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of 'numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame.
This article is part of the themed issue 'Optical orbital angular momentum'.
Multiphoton Effects Enhanced due to Ultrafast Photon-Number Fluctuations
Kirill Yu. Spasibko, Denis A. Kopylov, Victor L. Krutyanskiy, Tatiana V. Murzina, Gerd Leuchs, Maria V. Chekhova
The rate of an n-photon effect generally scales as the nth order autocorrelation function of the incident light, which is high for light with strong photon-number fluctuations. Therefore, "noisy" light sources are much more efficient for multiphoton effects than coherent sources with the same mean power, pulse duration, and repetition rate. Here we generate optical harmonics of the order of 2-4 from a bright squeezed vacuum, a state of light consisting of only quantum noise with no coherent component. We observe up to 2 orders of magnitude enhancement in the generation of optical harmonics due to ultrafast photon-number fluctuations. This feature is especially important for the nonlinear optics of fragile structures, where the use of a noisy pump can considerably increase the effect without overcoming the damage threshold.
Laser-Patterning Engineering for Perovskite Solar Modules With 95% Aperture Ratio
Alessandro Lorenzo Palma, Fabio Matteocci, Antonio Agresti, Sara Pescetelli, Emanuele Calabro, Luigi Vesce, Silke Christiansen, Michael Schmidt, Aldo Di Carlo
IEEE JOURNAL OF PHOTOVOLTAICS
7(6)
1674-1680
(2017)
|
Journal
Small area hybrid organometal halide perovskite based solar cells reached performances comparable to the multicrystalline silicon wafer cells. However, industrial applications require the scaling-up of devices to module-size. Here, we report the first fully laser-processed large area (14.5 cm(2)) perovskite solar module with an aperture ratio of 95% and a power conversion efficiency of 9.3%. To obtain this result, we carried out thorough analyses and optimization of three laser processing steps required to realize the serial interconnection of various cells. By analyzing the statistics of the fabricated modules, we show that the error committed over the projected interconnection dimensions is sufficiently low to permit even higher aperture ratios without additional efforts.
Interaction Between Dirac Solitons and Jackiw-Rebbi States in Binary Waveguide Arrays
Truong X. Tran, Dung C. Duong, Fabio Biancalana
JOURNAL OF LIGHTWAVE TECHNOLOGY
35(23)
5092-5097
(2017)
|
Journal
We systematically study different scenarios of collision between Dirac solitons and Jackiw-Rebbi (JR) states, which have been found recently in a system consisting of two interfaced binary waveguide arrays with opposite propagation mismatches. This collision has the resonance features for the reflected and transmitted signals. The trapping effect of Dirac solitons between two JR-states is analyzed.
Detection Loss Tolerant Supersensitive Phase Measurement with an SU(1,1) Interferometer
Mathieu Manceau, Gerd Leuchs, Farid Khalili, Maria Chekhova
In an unseeded SU(1,1) interferometer composed of two cascaded degenerate parametric amplifiers, with direct detection at the output, we demonstrate a phase sensitivity overcoming the shot noise limit by 2.3 dB. The interferometer is strongly unbalanced, with the parametric gain of the second amplifier exceeding the gain of the first one by a factor of 2, which makes the scheme extremely tolerant to detection losses. We show that by increasing the gain of the second amplifier, the phase supersensitivity of the interferometer can be preserved even with detection losses as high as 80%. This finding can considerably improve the state-of-the-art interferometry, enable sub-shot-noise phase sensitivity in spectral ranges with inefficient detection, and allow extension to quantum imaging.
Fluorescence intermittency originates from reclustering in
two-dimensional organic semiconductors
Anthony Ruth, Michitoshi Hayashi, Peter Zapol, Jixin Si, Matthew P. McDonald, Yurii V. Morozov, Masaru Kuno, Boldizsar Janko
Fluorescence intermittency or blinking is observed in nearly all nanoscale fluorophores. It is characterized by universal power-law distributions in on- and off-times as well as 1/f behaviour in corresponding emission power spectral densities. Blinking, previously seen in confined zero- and one-dimensional systems has recently been documented in two-dimensional reduced graphene oxide. Here we show that unexpected blinking during graphene oxide-to-reduced graphene oxide photoreduction is attributed, in large part, to the redistribution of carbon sp(2) domains. This reclustering generates fluctuations in the number/size of emissive graphenic nanoclusters wherein multiscale modelling captures essential experimental aspects of reduced graphene oxide's absorption/emission trajectories, while simultaneously connecting them to the underlying photochemistry responsible for graphene oxide's reduction. These simulations thus establish causality between currently unexplained, long timescale emission intermittency in a quantum mechanical fluorophore and identifiable chemical reactions that ultimately lead to switching between on and off states.
Dimensionality of random light fields
Andreas Norrman, Ari T. Friberg, Jose J. Gil, Tero Setala
JOURNAL OF THE EUROPEAN OPTICAL SOCIETY-RAPID PUBLICATIONS
13
36
(2017)
|
Journal
Background: The spectral polarization state and dimensionality of random light are important concepts in modern optical physics and photonics.
Methods: By use of space-frequency domain coherence theory, we establish a rigorous classification for the electricfield vector to oscillate in one, two, or three spatial dimensions.
Results: We also introduce a new measure, the polarimetric dimension, to quantify the dimensional character of light. The formalism is utilized to show that polarized three-dimensional light does not exist, while an evanescent wave generated in total internal reflection generally is a genuine three-dimensional light field.
Conclusions: The framework we construct advances the polarization theory of random light and it could be beneficial for near-field optics and polarization-sensitive applications involving complex-structured light fields.
Free space excitation of coupled Anderson-localized modes in photonic
crystal waveguides with polarization tailored beam
Ali Mahdavi, Paul Roth, Jolly Xavier, Taofiq K. Paraiso, Peter Banzer, Frank Vollmer
We experimentally demonstrate free space excitation of coupled Anderson-localized modes in photonic crystal (PhC) line-defect waveguides (W1) with polarization tailored beams. The corresponding light beam is tightly focused on a pristine W1, and out-of-plane scattering is imaged. By integrating the scattering spectra along the guide, at the W1 modal cut-off, Anderson-localized cavities are observed due to residual W1 fabrication-disorder. Their spectral lines exhibit high quality Q factors up to 2 x 10(5). The incident beam polarization and scattering intensities of the localized modes characterize the efficiency of free-space coupling. The coupling is studied for linearly and radially polarized input beams and for different input coupling locations along the W1 guide. The proposed coupling scheme is particularly attractive for excitation of PhC waveguide modes and Anderson-localized cavities by beam steering and scanning microscopy for sensing applications. Published by AIP Publishing.
Roadmap on structured light
Halina Rubinsztein-Dunlop, Andrew Forbes, M. V. Berry, M. R. Dennis, David L. Andrews, Masud Mansuripur, Cornelia Denz, Christina Alpmann, Peter Banzer, et al.
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.
High average power and single-cycle pulses from a mid-IR optical parametric chirped pulse amplifier
Ugaitz Elu, Matthias Baudisch, Hugo Pires, Francesco Tani, Michael H. Frosz, Felix Koettig, Alexey Ermolov, Philip St J. Russell, Jens Biegert
In attosecond and strong-field physics, the acquisition of data in an acceptable time demands the combination of high peak power with high average power. We report a 21 W mid-IR optical parametric chirped pulse amplifier (OPCPA) that generates 131 mu J and 97 fs (sub-9-cycle) pulses at a 160 kHz repetition rate and at a center wavelength of 3.25 mu m. Pulse-to-pulse stability of the carrier envelope phase (CEP)-stable output is excellent with a 0.33% rms over 288 million pulses (30 min) and compression close to a single optical cycle was achieved through soliton self-compression inside a gas-filled mid-IR antiresonant-guiding photonic crystal fiber. Without any additional compression device, stable generation of 14.5 fs (1.35-optical-cycle) pulses was achieved at an average power of 9.6 W. The resulting peak power of 3.9 GW in combination with the near-single-cycle duration and intrinsic CEP stability makes our OPCPA a key-enabling technology for the next generation of extreme photonics, strong-field attosecond research, and coherent x-ray science. (C) 2017 Optical Society of America
Hybrid photonic-crystal fiber
Christos Markos, John C. Travers, Amir Abdolvand, Benjamin J. Eggleton, Ole Bang
REVIEWS OF MODERN PHYSICS
89(4)
045003
(2017)
|
Journal
This article offers an extensive survey of results obtained using hybrid photonic-crystal fibers (PCFs) which constitute one of the most active research fields in contemporary fiber optics. The ability to integrate novel and functional materials in solid-and hollow-core PCFs through various postprocessing methods has enabled new directions toward understanding fundamental linear and nonlinear phenomena as well as novel application aspects, within the fields of optoelectronics, material and laser science, remote sensing, and spectroscopy. Here the recent progress in the field of hybrid PCFs is reviewed from scientific and technological perspectives, focusing on how different fluids, solids, and gases can significantly extend the functionality of PCFs. The first part of this review discusses the efforts to develop tunable linear and nonlinear fiber-optic devices using PCFs infiltrated with various liquids, glasses, semiconductors, and metals. The second part concentrates on recent and state-of-the-art advances in the field of gas-filled hollow-core PCFs. Extreme ultrafast gas-based nonlinear optics toward light generation in the extreme wavelength regions of vacuum ultraviolet, pulse propagation, and compression dynamics in both atomic and molecular gases, and novel soliton-plasma interactions are reviewed. A discussion of future prospects and directions is also included.
Generation of unipolar pulses in nonlinear media
R. M. Arkhipov, A. V. Pakhomov, M. V. Arkhipov, I. Babushkin, Yu. A. Tolmachev, N. N. Rosanov
Methods recently proposed for generating unipolar pulses in nonlinear media in terahertz and optical electromagnetic ranges are reviewed. Such pulses have nonzero "electric area" (time integral of the field strength over the entire duration of a pulse) and, correspondingly, a significant component of the field with zero frequency, thus exhibiting quasistatic properties. Effective generation of unipolar pulses would allow, e.g., transferring mechanical momentum to charged particles and, thereby, controlling the motion of wave packets of matter, which can be useful for compact accelerators of charged particles and for other applications.
Progress toward optimal quantum tomography with unbalanced homodyning
Balanced homodyning, heterodyning, and unbalanced homodyning are three well-known sampling techniques used in quantum optics to characterize photonic sources in the continuous-variable regime. We show that for all quantum states and all observable-parameter tomography schemes, which includes reconstructions of arbitrary operator moments and phase-space quasidistributions, localized sampling with unbalanced homodyning is always tomographically more powerful (gives more accurate estimators) than delocalized sampling with heterodyning. The latter is recently known to often give more accurate parameter reconstructions than conventional marginalized sampling with balanced homodyning. This result also holds for realistic photodetectors with subunit efficiency. With examples from first-through fourth-moment tomography, we demonstrate that unbalanced homodyning can outperform balanced homodyning when heterodyning fails to do so. This new benchmark takes us one step towards optimal continuous-variable tomography with conventional photodetectors and minimal experimental components.
Superiority of heterodyning over homodyning: An assessment with
quadrature moments
Y. S. Teo, C. R. Mueller, H. Jeong, Z. Hradil, J. Rehacek, L. L. Sanchez-Soto
We examine the moment-reconstruction performance of both the homodyne and heterodyne (doublehomodyne) measurement schemes for arbitrary quantum states and introduce moment estimators that optimize the respective schemes for any given data. In the large-data limit, these estimators are as efficient as the maximum-likelihood estimators. We then illustrate the superiority of the heterodyne measurement for the reconstruction of the first and second moments by analyzing Gaussian states and many other significant nonclassical states. Finally, we present an extension of our theories to two-mode sources, which can be straightforwardly generalized to all other multimode sources.
Photochemistry in a soft-glass single-ring hollow-core photonic crystal fibre
Ana M. Cubillas, Xin Jiang, Tijmen G. Euser, Nicola Taccardi, Bastian J. M. Etzold, Peter Wasserscheid, Philip St. J. Russell
A hollow-core photonic crystal fibre (HC-PCF), guided by photonic bandgap effects or anti-resonant reflection, offers strong light confinement and long photochemical interaction lengths in a microscale channel filled with a solvent of refractive index lower than that of glass (usually fused silica). These unique advantages have motivated its recent use as a highly efficient and versatile microreactor for liquid-phase photochemistry and catalysis. In this work, we use a single-ring HC-PCF made from a high-index soft glass, thus enabling photochemical experiments in higher index solvents. The optimized light-matter interaction in the fibre is used to strongly enhance the reaction rate in a proof-of-principle photolysis reaction in toluene.
Polarization-Selective Out-Coupling of Whispering-Gallery Modes
Florian Sedlmeir, Matthew R. Foreman, Ulrich Vogl, Richard Zeltner, Gerhard Schunk, Dmitry V. Strekalov, Christoph Marquardt, Gerd Leuchs, Harald G. L. Schwefel
Whispering-gallery mode (WGM) resonators are an important platform for linear, nonlinear, and quantum optical experiments. In such experiments, independent control of in-coupling and out-coupling rates to different modes can lead to higher conversion efficiencies and greater flexibility in the generation of nonclassical states based on parametric down-conversion. In this work, we introduce a scheme that enables selective out-coupling of WGMs belonging to a specific polarization family, while the orthogonally polarized modes remain largely unperturbed. Our technique utilizes material birefringence in both the resonator and the coupler such that a negative (positive) birefringence allows for polarization-selective coupling to TE (TM) WGMs. We formulate a refined coupling condition suitable for describing the case where the refractive indices of the resonator and the coupler are almost the same, from which we derive a criterion for polarization-selective coupling. Finally, we experimentally demonstrate our proposed method using a lithium niobate disk resonator coupled to a lithium niobate prism, where we show a 22-dB suppression of coupling to TM modes relative to TE modes.
Label-free optical detection of single enzyme-reactant reactions and
associated conformational changes
Eugene Kim, Martin D. Baaske, Isabel Schuldes, Peter S. Wilsch, Frank Vollmer
Monitoring the kinetics and conformational dynamics of single enzymes is crucial to better understand their biological functions because these motions and structural dynamics are usually unsynchronized among the molecules. However, detecting the enzyme-reactant interactions and associated conformational changes of the enzyme on a single-molecule basis remains as a challenge to established optical techniques because of the commonly required labeling of the reactants or the enzyme itself. The labeling process is usually nontrivial, and the labels themselves might skew the physical properties of the enzyme. We demonstrate an optical, label-free method capable of observing enzymatic interactions and associated conformational changes on a single-molecule level. We monitor polymerase/DNA interactions via the strong near-field enhancement provided by plasmonic nanorods resonantly coupled to whispering gallery modes in microcavities. Specifically, we use two different recognition schemes: one in which the kinetics of polymerase/DNA interactions are probed in the vicinity of DNA-functionalized nanorods, and the other in which these interactions are probed via the magnitude of conformational changes in the polymerase molecules immobilized on nanorods. In both approaches, we find that low and high polymerase activities can be clearly discerned through their characteristic signal amplitude and signal length distributions. Furthermore, the thermodynamic study of the monitored interactions suggests the occurrence of DNA polymerization. This work constitutes a proof-of-concept study of enzymatic activities using plasmonically enhanced microcavities and establishes an alternative and label-free method capable of investigating structural changes in single molecules.
Unconstrained Capacities of Quantum Key Distribution and Entanglement
Distillation for Pure-Loss Bosonic Broadcast Channels
Masahiro Takeoka, Kaushik P. Seshadreesan, Mark M. Wilde
We consider quantum key distribution (QKD) and entanglement distribution using a single-sender multiple-receiver pure-loss bosonic broadcast channel. We determine the unconstrained capacity region for the distillation of bipartite entanglement and secret key between the sender and each receiver, whenever they are allowed arbitrary public classical communication. A practical implication of our result is that the capacity region demonstrated drastically improves upon rates achievable using a naive time-sharing strategy, which has been employed in previously demonstrated network QKD systems. We show a simple example of a broadcast QKD protocol overcoming the limit of the point-to-point strategy. Our result is thus an important step toward opening a new framework of network channel-based quantum communication technology.
The emission rate of a point dipole can be strongly increased in the presence of a well-designed optical antenna. Yet, optical antenna design is largely based on radio-frequency rules, ignoring, e.g., Ohmic losses and non-negligible field penetration in metals at optical frequencies. Here, we combine reciprocity and Poynting's theorem to derive a set of optical-frequency antenna design rules for benchmarking and optimizing the performance of optical antennas driven by single quantum emitters. Based on these findings a novel plasmonic cavity antenna design is presented exhibiting a considerably improved performance compared to a reference two-wire antenna. Our work will be useful for the design of high-performance optical antennas and nanoresonators for diverse applications ranging from quantum optics to antenna-enhanced single-emitter spectroscopy and sensing.
Experimental realization of an absolute single-photon source based on a
single nitrogen vacancy center in a nanodiamond
Beatrice Rodiek, Marco Lopez, Helmuth Hofer, Geiland Porrovecchio, Marek Smid, Xiao-Liu Chu, Stephan Gotzinger, Vahid Sandoghdar, Sarah Lindner, et al.
We report on the experimental realization of an absolute single-photon source based on a single nitrogen vacancy (NV) center in a nanodiamond at room temperature and on the calculation of its absolute spectral photon flux from experimental data. The single-photon source was calibrated with respect to its photon flux and its spectral photon rate density. The photon flux was measured with a low-noise silicon photodiode traceable to the primary standard for optical flux, taking into account the absolute spectral power distribution using a calibrated spectroradiometer. The optical radiant flux is adjustable from 55 fW, which is almost the lowest detection limit for the silicon photodiode, and 75 fW, which is the saturation power of the NV center. These fluxes correspond to total photon flux rates between 190,000 photons per second and 260,000 photons per second, respectively. The single-photon emission purity is indicated by a g((2))(0) value, which is between 0.10 and 0.23, depending on the excitation power. To our knowledge, this is the first single-photon source absolutely calibrated with respect to its absolute optical radiant flux and spectral power distribution, traceable to the corresponding national standards via an unbroken traceability chain. The prospects for its application, e.g., for the detection efficiency calibration of single-photon detectors as well as for use as a standard photon source in the low photon flux regime, are promising. (C) 2017 Optical Society of America
Population density gratings induced by few-cycle optical pulses in a resonant medium
R. M. Arkhipov, A. V. Pakhomov, M. V. Arkhipov, I. Babushkin, A. Demircan, U. Morgner, N. N. Rosanov
Creation, erasing and ultrafast control of population density gratings using few-cycle optical pulses coherently interacting with resonant medium is discussed. In contrast to the commonly used schemes, here the pulses do not need to overlap in the medium, interaction between the pulses is mediated by excitation of polarization waves. We investigate the details of the dynamics arising in such ultrashort pulse scheme and develop an analytical theory demonstrating the importance of the phase memory effects in the dynamics.
Extremely broadband single-shot cross-correlation frequency-resolved optical gating using a transient grating as gate and dispersive element
H. Valtna-Lukner, F. Belli, A. Ermolov, F. Koettig, K. F. Mak, F. Tani, J. C. Travers, P. St. J. Russell
REVIEW OF SCIENTIFIC INSTRUMENTS
88(7)
073106
(2017)
|
Journal
Across-correlation frequency-resolved optical gating (FROG) concept, potentially suitable for characterizing few or sub-cycle pulses in a single shot, is described in which a counter-propagating transient grating is used as both the gate and the dispersive element in a FROG spectrometer. An all-reflective setup, which can operate over the whole transmission range of the nonlinear medium, within the sensitivity range of the matrix sensor, is also proposed, and proof-of-principle experiments for the ultraviolet and visible-to-near-infrared spectral ranges are reported. Published by AIP Publishing.
Characterization and shaping of the time-frequency Schmidt mode spectrum
of bright twin beams generated in gas-filled hollow-core photonic
crystal fibers
M. A. Finger, N. Y. Joly, P. St. J. Russell, M. V. Chekhova
We vary the time-frequency mode structure of ultrafast pulse-pumped modulational instability (MI) twin beams in an argon-filled hollow-core kagome-style photonic crystal fiber by adjusting the pressure, pump pulse chirp, fiber length, and parametric gain. Compared to solid-core systems, the pressure-dependent dispersion landscape brings increased flexibility to the tailoring of frequency correlations, and we demonstrate that the pump pulse chirp can be used to tune the joint spectrum of femtosecond-pumped.(3) sources. We also characterize the resulting mode content, not only by measuring the multimode second-order correlation function g((2)), but also by directly reconstructing the shapes and weights of time-frequency Schmidt (TFS) modes. We show that the number of modes directly influences the shot-to-shot pulse-energy and spectral-shape fluctuations in MI. Using this approach we control and monitor the number of TFS modes within the range from 1.3 to 4 using only a single fiber.
Understanding GaN/InGaN core-shell growth towards high quality factor
whispering gallery modes from non-polar InGaN quantum wells on GaN rods
C. Tessarek, S. Rechberger, C. Dieker, M. Heilmann, E. Spiecker, S. Christiansen
GaN microrods are used as a basis for subsequent InGaN quantum well (QW) and quantum dot deposition by metal-organic vapor phase epitaxy. The coverage of the shell along the sidewall of rods is dependent on the rod growth time and a complete coverage is obtained for shorter rod growth times. Transmission electron microscopy measurements are performed to reveal the structural properties of the InGaN layer on the sidewall facet and on the top facet. The presence of layers in the microrod and on the microrod surface will be discussed with respect to GaN and InGaN growth. A detailed model will be presented explaining the formation of multiple SiN layers and the partial and full coverage of the shell around the core. Cathodoluminescence measurements are performed to analyze the InGaN emission properties along the microrod and to study the microresonator properties of such hexagonal core-shell structures. High quality factor whispering gallery modes with Q similar to 1200 are reported for the first time in a GaN microrod/InGaN non-polar QW core-shell geometry. The GaN/InGaN core-shell microrods are expected to be promising building blocks for low-threshold laser diodes and ultra-sensitive optical sensors.
Temporal shaping of single photons enabled by entanglement
Valentin Averchenko, Denis Sych, Gerhard Schunk, Ulrich Vogl, Christoph Marquardt, Gerd Leuchs
We present a method to produce pure single photons with an arbitrary designed temporal shape in a heralded way. As an indispensable resource, the method uses pairs of time-energy entangled photons. One photon of a pair undergoes temporal amplitude-phase modulation according to the desired shape. Subsequent frequency-resolved detection of the modulated photon heralds its entangled counterpart in a pure quantum state. The temporal shape of the heralded photon is indirectly affected by the modulation in the heralding arm. We derive conditions for which the shape of the heralded photon is given by the modulation function. The method can be implemented with various sources of time-energy entangled photons. In particular, using entangled photons from parametric down-conversion the method provides a simple means to generate pure shaped photons with an unprecedented broad range of temporal durations, from tenths of femtoseconds to microseconds. This shaping of single photons will push forward the implementation of scalable multidimensional quantum information protocols, efficient photon-matter coupling, and quantum control at the level of single quanta.
Fundamental limits of optical force and torque
A. Rahimzadegan, Rasoul Alaee Khanghah, I. Fernandez-Corbaton, C. Rockstuhl
Optical force and torque provide unprecedented control on the spatial motion of small particles. A valid scientific question, that has many practical implications, concerns the existence of fundamental upper bounds for the achievable force and torque exerted by a plane wave illumination with a given intensity. Here, while studying isotropic particles, we show that different light-matter interaction channels contribute to the exerted force and torque, and analytically derive upper bounds for each of the contributions. Specific examples for particles that achieve those upper bounds are provided. We study how and to which extent different contributions can add up to result in the maximum optical force and torque. Our insights are important for applications ranging from molecular sorting, particle manipulation, and nanorobotics up to ambitious projects such as laser-propelled spaceships.
Stabilization of class-B broad-area laser emission by external optical
injection
A. V. Pakhomov, R. M. Arkhipov, N. E. Molevich
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
34(4)
756-763
(2017)
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Journal
We theoretically examine the effect of external optical injection on the spatiotemporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active medium. Stabilizing action of optical injection is shown to be closely related to the suppression of inherent relaxation oscillations behavior. (C) 2017 Optical Society of America
Linear and angular momenta in tightly focused vortex segmented beams of light
Martin Neugebauer, Andrea Aiello, Peter Banzer
Chinese Optics Letters
15(3)
030003
(2017)
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Journal
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PDF
We investigate the linear momentum density of light, which can be decomposed into spin and orbital parts, in the complex three-dimensional field distributions of tightly focused vortex segmented beams. The chosen angular spectrum exhibits two spatially separated vortices of opposite charge and orthogonal circular polarization to generate phase vortices in a meridional plane of observation. In the vicinity of those vortices, regions of negative orbital linear momentum occur. Besides these phase vortices, the occurrence of transverse orbital angular momentum manifests in a vortex charge-dependent relative shift of the energy density and linear momentum density.
Publikationen des Max-Planck-Instituts für die Physik des Lichts
2017
Publikationen
Max-Planck-Zentren und -Schulen
Datenerfassung
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