Ultra-Short Laser Surface Properties Optimization of Biocompatibility Characteristics of 3D Poly-ε-Caprolactone and Hydroxyapatite Composite Scaffolds
Albena Daskalova,
Emil Filipov,
Liliya Angelova,
Radostin Stefanov,
Dragomir Tatchev,
Georgi Avdeev,
Lamborghini Sotelo,
Silke Christiansen,
George Sarau, et al.
The use of laser processing for the creation of diverse morphological patterns onto the surface of polymer scaffolds represents a method for overcoming bacterial biofilm formation and inducing enhanced cellular dynamics. We have investigated the influence of ultra-short laser parameters on 3D-printed poly-epsilon-caprolactone (PCL) and poly-epsilon-caprolactone/hydroxyapatite (PCL/HA) scaffolds with the aim of creating submicron geometrical features to improve the matrix biocompatibility properties. Specifically, the present research was focused on monitoring the effect of the laser fluence (F) and the number of applied pulses (N) on the morphological, chemical and mechanical properties of the scaffolds. SEM analysis revealed that the femtosecond laser treatment of the scaffolds led to the formation of two distinct surface geometrical patterns, microchannels and single microprotrusions, without triggering collateral damage to the surrounding zones. We found that the microchannel structures favor the hydrophilicity properties. As demonstrated by the computer tomography results, surface roughness of the modified zones increases compared to the non-modified surface, without influencing the mechanical stability of the 3D matrices. The X-ray diffraction analysis confirmed that the laser structuring of the matrices did not lead to a change in the semi-crystalline phase of the PCL. The combinations of two types of geometrical designs-wood pile and snowflake-with laser-induced morphologies in the form of channels and columns are considered for optimizing the conditions for establishing an ideal scaffold, namely, precise dimensional form, mechanical stability, improved cytocompatibility and antibacterial behavior.
Dispersion Tailoring and Four-Wave Mixing in Silica Microspheres with Germanosilicate Coating
Maria P. Marisova,
Alexey Andrianov V,
Gerd Leuchs,
Elena A. Anashkina
Optical whispering gallery mode microresonators with controllable parameters in the telecommunication range are demanded for diverse applications. Controlling group velocity dispersion (GVD) in microresonators is an important problem, as near-zero GVD in a broad wavelength range could contribute to the development of new microresonator-based light sources. We demon-strated theoretically near-zero dispersion tailoring in the SCL-band in combination with free-spectral range (FSR) optimization for FSR = 200 GHz and 300 GHz in silica glass microspheres with micronscale germanosilicate coating. As an illustration of a possible application of such a GVD, we also performed a theoretical study of degenerate four-wave mixing (FWM) processes in the proposed microresonators for pumping in the SCL-band. We found that in some cases the generation of two or even three pairs of waves-satellites in a FWM process is possible in principle due to the specific GVD features. We also determined optimal microresonator configurations for achieving gradual change in the satellite frequency shift for the pump wavelengths in the SCL-, S-, CL-, C-, and L-bands. The maximum obtained FWM satellite tunability span was similar to 78 THz for a pump wavelength change of similar to 30 nm, which greatly exceeds the results for a regular silica microsphere without coating.
Benchmarking quantum tomography completeness and fidelity with machine learning
Yong Siah Teo,
Seongwook Shin,
Hyunseok Jeong,
Yosep Kim,
Yoon-Ho Kim,
Gleb Struchalin I,
Egor Kovlakov V,
Stanislav S. Straupe,
Sergei P. Kulik, et al.
NEW JOURNAL OF PHYSICS
23
(10)
103021
(2021)
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| PDF
We train convolutional neural networks to predict whether or not a set of measurements is informationally complete to uniquely reconstruct any given quantum state with no prior information. In addition, we perform fidelity benchmarking based on this measurement set without explicitly carrying out state tomography. The networks are trained to recognize the fidelity and a reliable measure for informational completeness. By gradually accumulating measurements and data, these trained convolutional networks can efficiently establish a compressive quantum-state characterization scheme by accelerating runtime computation and greatly reducing systematic drifts in experiments. We confirm the potential of this machine-learning approach by presenting experimental results for both spatial-mode and multiphoton systems of large dimensions. These predictions are further shown to improve when the networks are trained with additional bootstrapped training sets from real experimental data. Using a realistic beam-profile displacement error model for Hermite-Gaussian sources, we further demonstrate numerically that the orders-of-magnitude reduction in certification time with trained networks greatly increases the computation yield of a large-scale quantum processor using these sources, before state fidelity deteriorates significantly.
Quantum noise squeezing of CW light in tellurite glass fibres
E. A. Anashkina,
A. A. Sorokin,
Gerd Leuchs,
A. V. Andrianov
RESULTS IN PHYSICS
30
104843
(2021)
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| PDF
Light with suppressed quantum fluctuations is desirable for a lot of applications. There are several approaches to suppress a noise including Kerr squeezing in optical fibres. Silica fibres are commonly used for this purpose. Here we propose to use highly nonlinear tellurite glass fibres for Kerr squeezing of CW laser field and demonstrate by simulations in the framework of the stochastic generalized nonlinear Schrodinger equation the possibility of -20 dB noise suppression. In simulations, Raman terms and losses are switched on and switched off to find their contributions to the limits of squeezing. The analytical estimates without loss and with lumped loss are also given.
Optical Frequency Combs Generated in Silica Microspheres in the Telecommunication C-, U-, and E-Bands
Elena A. Anashkina,
Maria P. Marisova,
Toms Salgals,
Janis Alnis,
Ilya Lyashuk,
Gerd Leuchs,
Sandis Spolitis,
Vjaceslavs Bobrovs,
Alexey V. Andrianov
Optical frequency combs (OFCs) generated in microresonators with whispering gallery modes are demanded for different applications including telecommunications. Extending operating spectral ranges is an important problem for wavelength-division multiplexing systems based on microresonators. We demonstrate experimentally three spectrally separated OFCs in the C-, U-, and E-bands in silica microspheres which, in principle, can be used for telecommunication applications. For qualitative explanation of the OFC generation in the sidebands, we calculated gain coefficients and gain bandwidths for degenerate four-wave mixing (FWM) processes. We also attained a regime when the pump frequency was in the normal dispersion range and only two OFCs were generated. The first OFC was near the pump frequency and the second Raman-assisted OFC with a soliton-like spectrum was in the U-band. Numerical simulation based on the Lugiato-Lefever equation was performed to support this result and demonstrate that the Raman-assisted OFC may be a soliton.
Laser-induced switching of the biological activity of phosphonate molecules
NEW JOURNAL OF CHEMISTRY
45
(34)
15195-15199
(2021)
| Journal
Butyrylcholinesterase inhibition and its enhancement as a result of laser irradiation are demonstrated for the first time for a series of phosphorylated arylaminomalonates. The effect of substituents in the phenyl group on butyrylcholinesterase inhibition and its laser-activated enhancement is revealed experimentally and confirmed by molecular dynamics and docking modelling.
Effects of coherence on temporal resolution
Syamsundar De,
Jano Gil-Lopez,
Benjamin Brecht,
Christine Silberhorn,
Luis Sanchez-Soto,
Zdeněk Hradil,
Jaroslav Řeháček
Physical Review Research
3
033082
(2021)
| Journal
| PDF
Measuring small separations between two optical sources, either in space or in time, constitutes an important metrological challenge as standard intensity-only measurements fail for vanishing separations. Contrarily, it has been established that appropriate coherent mode projections can appraise arbitrarily small separations with quantum-limited precision. However, the question of whether the optical coherence brings any metrological advantage to mode projections is still a point of debate. Here, we elucidate this problem by experimentally investigating the effect of varying coherence on estimating the temporal separation between two single-photon pulses. We show that, for an accurate interpretation, special attention must be paid to properly normalize the quantum Fisher information to account for the strength of the signal.
Thermal noise in electro-optic devices at cryogenic temperatures
Sonia Mobassem,
Nicholas J. Lambert,
Alfredo Rueda,
Johannes M. Fink,
Gerd Leuchs,
Harald G. L. Schwefel
QUANTUM SCIENCE AND TECHNOLOGY
6
(4)
045005
(2021)
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| PDF
The quantum bits (qubits) on which superconducting quantum computers are based have energy scales corresponding to photons with GHz frequencies. The energy of photons in the gigahertz domain is too low to allow transmission through the noisy room-temperature environment, where the signal would be lost in thermal noise. Optical photons, on the other hand, have much higher energies, and signals can be detected using highly efficient single-photon detectors. Transduction from microwave to optical frequencies is therefore a potential enabling technology for quantum devices. However, in such a device the optical pump can be a source of thermal noise and thus degrade the fidelity; the similarity of input microwave state to the output optical state. In order to investigate the magnitude of this effect we model the sub-Kelvin thermal behavior of an electro-optic transducer based on a lithium niobate whispering gallery mode resonator. We find that there is an optimum power level for a continuous pump, whilst pulsed operation of the pump increases the fidelity of the conversion.
Numerical Simulations on Polarization Quantum Noise Squeezing for Ultrashort Solitons in Optical Fiber with Enlarged Mode Field Area
Arseny A. Sorokin,
Elena A. Anashkina,
Joel F. Corney,
Vjaceslavs Bobrovs,
Gerd Leuchs,
Alexey Andrianov V
Broadband quantum noise suppression of light is required for many applications, including detection of gravitational waves, quantum sensing, and quantum communication. Here, using numerical simulations, we investigate the possibility of polarization squeezing of ultrashort soliton pulses in an optical fiber with an enlarged mode field area, such as large-mode area or multicore fibers (to scale up the pulse energy). Our model includes the second-order dispersion, Kerr and Raman effects, quantum noise, and optical losses. In simulations, we switch on and switch off Raman effects and losses to find their contribution to squeezing of optical pulses with different durations (0.1-1 ps). For longer solitons, the peak power is lower and a longer fiber is required to attain the same squeezing as for shorter solitons, when Raman effects and losses are neglected. In the full model, we demonstrate optimal pulse duration (similar to 0.4 ps) since losses limit squeezing of longer pulses and Raman effects limit squeezing of shorter pulses.
IM/DD WDM-PON Communication System Based on Optical Frequency Comb Generated in Silica Whispering Gallery Mode Resonator
Sandis Spolitis,
Rihards Murnieks,
Laura Skladova,
Toms Salgals,
Alexey V. Andrianov,
Maria P. Marisova,
Gerd Leuchs,
Elena A. Anashkina,
Vjaceslavs Bobrovs
This article reports an implementation of a microsphere-based optical frequency comb (OFC) generator for substitution of individual laser arrays and simulates wavelength division multiplexed passive optical network (WDM-PON) based on this OFC generator. Our proposed generator is built based on silica microsphere, barely studied for fiber optical communication systems, and is a promising solution with photonic integration capability. Kerr OFC as a multiple light source containing more than 20 spectral carriers in the fundamental mode family in the C-band and beyond is demonstrated experimentally. Four of these OFC generator carriers with the highest peak power are studied in simulated 4-channel 393 GHz spaced WDM-PON. Additionally, we show this OFC as a source of optical carriers capable of providing data transmission over most utilized fiber types in modern optical communication systems, namely, single-mode fiber (SMF), non-zero dispersion-shifted fiber (NZ-DSF), and cut-off shifted fiber (CSF). We show through the simulations that error-free data transmission is possible, providing a total transmission capacity of 40 Gbit/s by using four OFC generated carriers.
Microsphere kinematics from the polarization of tightly focused nonseparable light
Stefan Berg-Johansen,
Martin Neugebauer,
Andrea Aiello,
Gerd Leuchs,
Peter Banzer,
Christoph Marquardt
Recently, it was shown that vector beams can be utilized for fast kinematic sensing via measurements of their global polarization state [Optica 2, 864 (2015)]. The method relies on correlations between the spatial and polarization degrees of freedom of the illuminating field which result from its nonseparable mode structure. Here, we extend the method to the nonparaxial regime. We study experimentally and theoretically the far-field polarization state generated by the scattering of a dielectric microsphere in a tightly focused vector beam as a function of the particle position. Using polarization measurements only, we demonstrate position sensing of a Mie particle in three dimensions. Our work extends the concept of back focal plane interferometry and highlights the potential of polarization analysis in optical tweezers employing structured light.
Rotation sensing at the ultimate limit
Aaron Z Goldberg,
Andrei B Klimov,
Gerd Leuchs,
Luis Sanchez-Soto
Journal of Physics: Photonics
3
022008
(2021)
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| PDF
Conventional classical sensors are approaching their maximum sensitivity levels in many areas. Yet these levels are still far from the ultimate limits dictated by quantum mechanics. Quantum sensors promise a substantial step ahead by taking advantage of the salient sensitivity of quantum states to the environment. Here, we focus on sensing rotations, a topic of broad application. By resorting to the basic tools of estimation theory, we derive states that achieve the ultimate sensitivities in estimating both the orientation of an unknown rotation axis and the angle rotated about it. The critical enhancement obtained with these optimal states should make of them an indispensable ingredient in the next generation of rotation sensors that is now blossoming.
Axial superlocalization with vortex beams
D. Koutny,
Z. Hradil,
J. Rehacek,
Luis Sanchez-Soto
Quantum Science and Technology
6
(2)
025021
(2021)
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| PDF
Improving axial resolution is of paramount importance for three-dimensional optical imaging systems. Here, we investigate the ultimate precision in axial<br>localization using vortex beams. For Laguerre-Gauss beams, this limit can be achieved with just an intensity scan. The same is not true for superpositions<br>of Laguerre-Gauss beams, in particular for those with intensity profiles that rotate on defocusing. Microscopy methods based on rotating vortex beams may thus benefit from replacing traditional intensity sensors with advanced mode-sorting techniques.
Compensation-free high-dimensional free-space optical communication using turbulence-resilient vector beams
Ziyi Zhu,
Molly Janasik,
Alexander Fyffe,
Darrick Hay,
Yiyu Zhou,
Brian Kantor,
Taylor Winder,
Robert W. Boyd,
Gerd Leuchs, et al.
NATURE COMMUNICATIONS
12
(1)
1666
(2021)
| Journal
| PDF
Free-space optical communication is a promising means to establish versatile, secure and high-bandwidth communication between mobile nodes for many critical applications. While the spatial modes of light offer a degree of freedom to increase the information capacity of an optical link, atmospheric turbulence can introduce severe distortion to the spatial modes and lead to data degradation. Here, we demonstrate experimentally a vector-beam-based, turbulence-resilient communication protocol, namely spatial polarization differential phase shift keying (SPDPSK), that can reliably transmit high-dimensional information through a turbulent channel without the need of any adaptive optics for beam compensation. In a proof-of-principle experiment with a controllable turbulence cell, we measure a channel capacity of 4.84 bits per pulse using 34 vector modes through a turbulent channel with a scintillation index of 1.09, and 4.02 bits per pulse using 18 vector modes through even stronger turbulence corresponding to a scintillation index of 1.54. Resistance to turbulence is an ongoing challenge for point-to-point freespace communications. Here the authors present a protocol for encoding a large amount of information in vector beams that are transmittable through a moderately strong turbulent channel without adaptive beam compensation.
Quantum concepts in optical polarization
Aaron Z. Goldberg,
Pablo De La Hoz,
Gunnar Bjork,
Andrei B. Klimov,
Markus Grassl,
Gerd Leuchs,
Luis Sanchez-Soto
ADVANCES IN OPTICS AND PHOTONICS
13
(1)
1-73
(2021)
| Journal
We comprehensively review the quantum theory of the polarization properties of light. In classical optics, these traits are characterized by the Stokes parameters, which can be geometrically interpreted using the Poincare sphere. Remarkably, these Stokes parameters can also be applied to the quantum world, but then important differences emerge: now, because fluctuations in the number of photons are unavoidable, one is forced to work in the three-dimensional Poincare space that can be regarded as a set of nested spheres. Additionally, higher-order moments of the Stokes variables might play a substantial role for quantum states, which is not the case for most classical Gaussian states. This brings about important differences between these two worlds that we review in detail. In particular, the classical degree of polarization produces unsatisfactory results in the quantum domain. We compare alternative quantum degrees and put forth that they order various states differently. Finally, intrinsically nonclassical states are explored, and their potential applications in quantum technologies are discussed. (C) 2021 Optical Society of America.
Agile and versatile quantum communication: Signatures and secrets
Stefan Richter,
Matthew Thornton,
Imran Khan,
Hamish Scott,
Kevin Jaksch,
Ulrich Vogl,
Birgit Stiller,
Gerd Leuchs,
Christoph Marquardt, et al.
Agile cryptography allows for a resource-efficient swap of a cryptographic core in case the security of an underlying classical cryptographic algorithm becomes compromised. Conversely, versatile cryptography allows the user to switch the cryptographic task without requiring any knowledge of its inner workings.<br>In this paper, we suggest how these related principles can be applied to the field of quantum cryptography by explicitly demonstrating two quantum cryptographic protocols, quantum digital signatures (QDS) and quantum secret sharing (QSS), on the same hardware sender and receiver platform. Crucially, the protocols differ only in their classical postprocessing. The system is also suitable for quantum key distribution (QKD) and is highly compatible with deployed telecommunication infrastructures, since it uses standard quadrature phase-shift keying encoding and heterodyne detection. For the first time, QDS protocols are modified to allow for postselection at the receiver, enhancing protocol performance. The cryptographic primitives QDS and QSS are inherently multipartite, and we prove that they are secure not only when a player internal to the task is dishonest, but also when (external) eavesdropping on the quantum channel is allowed. In our first proof-of-principle demonstration of an agile and versatile quantum communication system, the quantum states are distributed at GHz rates. A 1-bit message may be securely signed using our QDS protocols in less than 0.05 ms over a 2-km fiber link and in less than 0.2 s over a 20-km fiber link. To our knowledge, this also marks the first demonstration of a continuous-variable direct QSS protocol.
SU(1, 1) covariant s-parametrized maps
Andrei B. Klimov,
Ulrich Seyfarth,
Hubert de Guise,
Luis Sanchez-Soto
Journal of Physics A
54
(6)
065301
(2021)
| Journal
We propose a practical recipe to compute the s-parametrized maps for systems with SU(1, 1) symmetry using a connection between the Q- and P-symbols through the action of an operator invariant under the group. This establishes equivalence relations between s-parametrized SU(1, 1)-covariant maps. The particular case of the self-dual (Wigner) phase-space functions, defined on the upper sheet of the two-sheet hyperboloid (or, equivalently, inside the Poincaré disc) are analysed.
Achieving the ultimate quantum timing resolution
Vahid Ansari,
Benjamin Brecht,
Jano Gil-López,
John M. Donohue,
Jaroslav Řeháček,
Zdeněk Hradil,
Luis Sanchez-Soto,
Christine Silberhorn
Accurate time-delay measurement is at the core of many modern technologies.<br>Here, we present a temporal-mode demultiplexing scheme that achieves the<br>ultimate quantum precision for the simultaneous estimation of the temporal<br>centroid, the time offset, and the relative intensities of an incoherent<br>mixture of ultrashort pulses at the single-photon level. We experimentally<br>resolve temporal separations ten times smaller than the pulse duration, as well<br>as imbalanced intensities differing by a factor of 10^2. This represents an<br>improvement of more than an order of magnitude over the best standard methods<br>based on intensity detection.<br>
Double-Sided Graphene-Enhanced Raman Scattering and Fluorescence Quenching in Hybrid Biological Structures
George Sarau,
Christoph Daniel,
Martin Heilmann,
Gerd Leuchs,
Kerstin Amann,
Silke H. Christiansen
Due to their large contact and loading surfaces as well as high sensitivities to chemical changes, graphene-based materials (GBMs) are increasingly being employed into novel nanomedicine technologies. Here biomolecule-monolayer graphene-kidney tissue hybrid structures are studied using mapping micro-Raman and fluorescence spectroscopies. Because in this configuration graphene interacts with molecules on both sides, a double-sided graphene-enhanced Raman scattering (GERS) effect up to approximate to 10.1 is found for biomolecules adsorbed on graphene and amino acids in the kidney tissue below graphene. Moreover, graphene causes an efficient autofluorescence quenching (FLQ) up to approximate to 20% emitted by the kidney tissue. Despite the complexity of such layered materials, the intriguing simultaneous occurrence of double-sided GERS (a new development of GERS) and FLQ phenomena can be well explained by suitable molecular structure and energy level alignment between molecules and graphene. These result in effective charge transfer mediated by non-covalent interactions as indicated by correlative strain, doping, and defect analyses in graphene based on the Raman data and energy level calculations. Last, the advantages of using graphene over standard photobleaching are demonstrated. This work can be extended to other macromolecular entities toward integrating GBMs in versatile drug delivery, imaging, and sensing devices.
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