Lifetime-limited zero-phonon spectra of single molecules in methyl methacrylate
A. Walser,
A. Renn,
Stephan Götzinger,
Vahid Sandoghdar
Chemical Physics Letters
472
44-47
(2009)
| Journal
We report on high resolution single molecule spectroscopy in frozen methyl methacrylate (MMA). We show that the zero-phonon transitions of single dibenzanthanthrene molecules in this polar matrix can reach their natural linewidth limit at T = 1.4 K. Our X-ray diffraction measurements and direct study of single molecule dipole orientation provide clear evidence for the crystalline nature of MMA at low temperatures. Our results hold promise for the controlled study of the transition between crystalline and amorphous matrices, and have implications on cryogenic single molecule microscopy in biological applications. (C) 2009 Elsevier B. V. All rights reserved.
Coherent state preparation and observation of Rabi oscillations in a single molecule
I. Gerhardt,
G. Wrigge,
G. Zumofen,
J. Hwang,
A. Renn,
Vahid Sandoghdar
We report on the excitation of single molecules via narrow zero-phonon transitions using short laser pulses. By monitoring the Stokes-shifted fluorescence, we studied the excited state population as a function of the delay time, laser intensity, and frequency detuning. A pi-pulse excitation was demonstrated with merely 500 photons, and 5 Rabi cycles were achieved at higher excitation powers. Our findings are in good agreement with theoretical calculations and provide a first step toward coherent manipulation of the electronic states of single molecules with few photons.
High-speed nanoscopic tracking of the position and orientation of a single virus
Philipp Kukura,
Helge Ewers,
Christian Mueller,
Alois Renn,
Ari Helenius,
Vahid Sandoghdar
Optical studies have revealed that, after binding, virions move laterally on the plasma membrane, but the complexity of the cellular environment and the drawbacks of fluorescence microscopy have prevented access to the molecular dynamics of early virus-host couplings, which are important for cell infection. Here we present a colocalization methodology that combines scattering interferometry and single-molecule fluorescence microscopy to visualize both position and orientation of single quantum dot-labeled Simian virus 40 (SV40) particles. By achieving nanometer spatial and 8 ms temporal resolution, we observed sliding and tumbling motions during rapid lateral diffusion on supported lipid bilayers, and repeated back and forth rocking between nanoscopic regions separated by 9 nm. Our findings suggest recurrent swap of receptors and viral pentamers as well as receptor aggregation in nanodomains. We discuss the prospects of our technique for studying virus-membrane interactions and for resolving nanoscopic dynamics of individual biological nano-objects.
Resolution and Enhancement in Nanoantenna-Based Fluorescence Microscopy
Hadi Eghlidi,
Kwang Geol Lee,
Xue-Wen Chen,
Stephan Götzinger,
Vahid Sandoghdar
Single gold nanoparticles can act as nanoantennas for enhancing the fluorescence of emitters in their near fields. Here we present experimental and theoretical studies of scanning antenna-based fluorescence microscopy as a function of the diameter of the gold nanoparticle. We examine the interplay between fluorescence enhancement and spatial resolution and discuss the requirements for deciphering single molecules in a dense sample. Resolutions better than 20 nm and fluorescence enhancement up to 30 times are demonstrated experimentally. By accounting for the tip shaft and the sample interface in finite-difference time-domain calculations, we explain why the measured fluorescence enhancements are higher in the presence of an interface than the values predicted for a homogeneous environment.
A single-molecule optical transistor
J. Hwang,
M. Pototschnig,
R. Lettow,
G. Zumofen,
A. Renn,
Stephan Götzinger,
Vahid Sandoghdar
The transistor is one of the most influential inventions of modern times and is ubiquitous in present-day technologies. In the continuing development of increasingly powerful computers as well as alternative technologies based on the prospects of quantum information processing, switching and amplification functionalities are being sought in ultrasmall objects, such as nanotubes, molecules or atoms(1-9). Among the possible choices of signal carriers, photons are particularly attractive because of their robustness against decoherence, but their control at the nano-metre scale poses a significant challenge as conventional nonlinear materials become ineffective. To remedy this shortcoming, resonances in optical emitters can be exploited, and atomic ensembles have been successfully used to mediate weak light beams(7). However, single-emitter manipulation of photonic signals has remained elusive and has only been studied in high-finesse microcavities(10-13) or waveguides(8,14). Here we demonstrate that a single dye molecule can operate as an optical transistor and coherently attenuate or amplify a tightly focused laser beam, depending on the power of a second 'gating' beam that controls the degree of population inversion. Such a quantum optical transistor has also the potential for manipulating non-classical light fields down to the single-photon level. We discuss some of the hurdles along the road towards practical implementations, and their possible solutions.
Spectral dynamics and spatial localization of single molecules in a polymer
A. Walser,
G. Zumofen,
A. Renn,
Stephan Götzinger,
Vahid Sandoghdar
We report on the high-resolution spectroscopy of single dibenzanthanthrene molecules embedded in polymethyl methacrylate (PMMA). We employed three methods for the characterization of spectral line shapes based on fitting a Lorentzian function, determining full widths at half-maxima, and calculation of the second-order spectral cumulant. The three approaches provide comparable histograms of linewidth distributions, displaying slowly decaying tails that are indicative of the Levy stable law. In addition, we introduce an alternative method for the analysis of spectral dynamics, in which ensemble spectra are reconstructed by adding single molecule spectral autocorrelations. Furthermore, we examine the spectral width and distributions of single molecules on the PMMA chain length over three orders of magnitude and find a very small dependence. Lastly, we demonstrate that, despite the strong spectral dynamics, it is possible to collect enough photons from single molecules to localize their positions to better than 10 nm.
We study the influence of a scanning nano-electrode on the fluorescence excitation spectra of single terrylene molecules embedded in thin p-terphenyl films at cryogenic temperatures. We show that applied voltages of less than 10 V can result in reversible Stark shifts of up to 100 times and a linewidth increase greater than 10 times the natural linewidth. We discuss the potential of our experimental scheme for the direct imaging of individual two-level systems in the nanometer vicinity of single molecules.
Circular Grating Resonators as Small Mode-Volume Microcavities for Switching
Sophie Schoenenberger,
Nikolaj Moll,
Thilo Stoeferle,
Rainer F. Mahrt,
Bert J. Offrein,
Stephan Götzinger,
Vahid Sandoghdar,
Jens Bolten,
Thorsten Wahlbrink,
Tobias Ploetzing,
Michael Waldow,
Michael Foerst
We demonstrate the suitability of microcavities based on circular grating resonators (CGRs) as fast switches. This type of optical resonator is characterized by a high quality factor and very small mode volume. The waveguide-coupled CGRs are fabricated with silicon-on-insulator technology compatible with standard complementary metal-oxide semiconductor (CMOS) processing. The linear optical properties of the CGRs are investigated by transmission spectroscopy. From 3D finite-difference time-domain simulations of isolated CGRs, we identify the measured resonances. We probe the spatial distribution and the parasitic losses of a resonant optical mode with scanning near-field optical microscopy. We observe fast all-optical switching within a few picoseconds by optically generating free charge carriers within the cavity. (C) 2009 Optical Society of America
Molecules as sources for indistinguishable single photons
Ville Ahtee,
Robert Lettow,
Robert Pfab,
Alois Renn,
Erkki Ikonen,
Stephan Götzinger,
Vahid Sandoghdar
Journal of Modern Optics
56
PII 907848818
161-166
(2009)
| Journal
We report on the triggered generation of identical photons by solid-state single-photon sources in two separate cryogenic laser scanning microscopes. Organic fluorescent molecules were used as emitters and investigated by means of high resolution laser spectroscopy. Continuous-wave photon correlation measurements on individual molecules proved the isolation of single quantum systems. By using frequency selective pulsed excitation of the molecule and efficient spectral filtering of its emission, we produced triggered Fourier-limited single photons. In a further step, local electric fields were applied to match the emission wavelengths of two different molecules via Stark effect. Identical single photons are indispensable for the realization of various quantum information processing schemes proposed. The solid-state approach presented here paves the way to the integration of multiple bright sources of single photons on a single chip.
Metal nanoparticles in strongly confined beams: transmission, reflection and absorption
Nassiredin M. Mojarad,
Gert Zumofen,
Vahid Sandoghdar,
Mario Agio
Journal of the European Optical Society Rapid Publications
4
09014
(2009)
| Journal
We investigate the interaction of tightly focused light with the surface-plasmon-polariton resonances of metal nanospheres. In particular, we compute the scattering and absorption ratios as well as transmission and reflection coefficients. Inspired by our previous work in [1], we discuss how well a metal nanoparticle approximates a point-like dipolar radiator. We find that a 100 nm silver nanosphere is very close to such an ideal oscillator. Our results have immediate implications for single nanoparticle spectroscopy and microscopy as well as plasmonics. [DOI: 10.2971/jeos.2009.09014]
Highly Efficient Interfacing of Guided Plasmons and Photons in Nanowires
Successful exploitations of strongly confined surface plasmon-polaritons critically rely on their efficient and rapid conversion to lossless channels. We demonstrate a simple, robust, and broadband butt-coupling technique for connecting a metallic nanowire and a dielectric nanofiber. Conversion efficiencies above 95% in the visible and close to 100% in the near-infrared can be achieved with realistic parameters. Moreover, by combining butt-coupling with nanofocusing, we propose a broadband high-throughput near-field optical microscope.
Imaging a Single Quantum Dot When It Is Dark
P. Kukura,
M. Celebrano,
A. Renn,
Vahid Sandoghdar
We have succeeded in recording extinction images of individual cadmium selenide quantum dots at ambient condition. This is achieved by optimizing the interference between the light that is coherently scattered from the quantum dot and the reflection of the incident laser beam. The ability to interrogate the dot in the absence of fluorescence has revealed that its extinction cross section diminishes in the photobleached state, but interestingly, it remains unchanged during fluorescence blinking off times. Our methodology makes optical imaging and spectroscopy accessible to the study of ultrasmall nanoscopic objects such as nonfluorescent macromolecules and single emitters with very low quantum efficiencies.
Gold, Copper, Silver and Aluminum Nanoantennas to Enhance Spontaneous Emission
A. Mohammadi,
Vahid Sandoghdar,
M. Agio
Journal of Computational and Theoretical Nanoscience
6
2024-2030
(2009)
| Journal
We compute the decay rates of emitters coupled to spheroidal nanoantennas made of gold, copper, silver, and aluminum. The spectral position of the localized surface plasmon-polariton resonance, the enhancement factors and the quantum efficiency are investigated as a function of the aspect ratio, background index and the metal composing the nanoantenna. While copper yields results similar to gold, silver and aluminum exhibit different performances. Our results show that with a careful choice of the parameters these nanoantennas can enhance emitters ranging from the UV to the near-IR spectrum.
Generation of total angular momentum eigenstates in remote qubits
A. Maser,
U. Schilling,
T. Bastin,
E. Solano,
C. Thiel,
J. von Zanthier
We propose a scheme enabling the universal coupling of angular momentum of N remote noninteracting qubits using linear optical tools only. Our system consists of N single-photon emitters in a Lambda configuration that are entangled among their long-lived ground-state qubits through suitably designed measurements of the emitted photons. In this manner, we present an experimentally feasible algorithm that is able to generate any of the 2(N) symmetric and nonsymmetric total angular momentum eigenstates spanning the Hilbert space of the N-qubit compound.
Spheroidal nanoparticles as nanoantennas for fluorescence enhancement
A. Mohammadi,
F. Kaminski,
Vahid Sandoghdar,
M. Agio
International Journal of Nanotechnology
6
902-914
(2009)
| Journal
Nanoantennas made of spheroidal metal nanoparticles are studied as a function of several parameters, namely aspect ratio, volume, background index and metal. Single nanospheroids are analysed using the polarisability theory with radiative and depolarisation corrections, while double spheroids are investigated using the finite-difference time-domain method. We focus on the spectral position of the plasmon resonance and on the scattering efficiency for applications related to the fluorescence enhancement of emitters. We show that a careful choice of the parameters allows covering wavelengths ranging from the UV to the near IR spectrum, while keeping the scattering efficiency close to 100%. We also discuss the role of the optical constants in determining the nanoantenna performances.
Pushing Optical Microscopy to the Limit: From Single‐Molecule Fluorescence Microscopy to Label‐Free Detection and Tracking of Biological Nano‐Objects
The promise and success of current biomedical research is highly dependent on understanding the mechanisms of fundamental biological processes such as protein folding, the function of molecular machines, or the interaction of proteins with molecular complexes. In particular, on the cellular level the heterogeneous and fluctuating environment as well as the intrinsic asynchronicity of protein function requires observation of individual copies rather than ensembles if a detailed understanding of their function is to be obtained. As a consequence, real‐time in vivo imaging is one of the most desirable tools for investigating biological systems at microscopic and nanoscopic levels. In this chapter, we summarize some of the recent advances in optical microscopy with a particular focus on the capabilities and limitations of studies at the single‐molecule and nanoparticle level. We present a detailed account of the intricate interplay between single‐molecule photophysical properties and the attainable signal‐to‐noise ratio in the ability to see, localize and trace single molecules. Furthermore, we discuss the possibility of single‐molecule labels being replaced by tiny light scatterers, such as gold nanoparticles, which offer an inherent photostability and lack of saturation. In particular, we introduce a novel interferometric technique for detecting nanoscopic objects and demonstrate its potential use both for the study of gold nanoparticle labels in scattering media and the label‐free detection of single biological nanoparticles in the absence of additional scatterers.
Contact
Nano-Optics Division Prof. Vahid Sandoghdar
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
