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  4. Vahid Sandoghdar

Prof. Vahid Sandoghdar

  • Director
  • Head of Nano-Optics Division

The research of our group aims to advance experimental and theoretical mastery of light-matter interaction at the nanometer scale and to achieve the same degree of control and finesse that is known from the gas-phase quantum optics in the condensed phase. To do this, we combine concepts from quantum optics, laser spectroscopy, cryogenics, optical imaging, scanning probe technology and nanofluidics. In this endeavour, we have addressed a wide spectrum of scientific questions, ranging from quantum optics to biophysics. For more information, please consult our research website and our list of publications.

2004

Tomographic plasmon spectroscopy of a single gold nanoparticle

Thomas Kalkbrenner, Ulf Hakanson, Vahid Sandoghdar

Nano Letters 4 2309-2314 (2004) | Journal

We demonstrate a tomographic method for determining the degree of ellipticity and the orientation of a gold nanoparticle. To do this, we attach a single nanoparticle to the end of a sharp glass fiber tip and record its plasmon spectra for different incident polarizations and angles of incidence. Our measurements allow us to identify the plasmon spectra along the three main axes of the particle, therefore resolving its "internal" spectral inhomogeneity. Knowledge of the plasmon resonances and the orientation of a metallic nanoparticle is an important asset for controlled and quantitative studies of its interaction with a single molecule.

Aligned terrylene molecules in a spin-coated ultrathin crystalline film of p-terphenyl

R.J. Pfab, J. Zimmermann, C. Hettich, Ilja Gerhardt, Alois Renn, Vahid Sandoghdar

Chemical Physics Letters 387 490-495 (2004) | Journal

We report on the use of a simple spin casting procedure to fabricate very thin crystalline films of P-terphenyl doped with fluorescent terrylene molecules. By performing single molecule studies, we show that the guest molecules are oriented normal to the plane of the film. We find that despite the very low thickness of the p-terphenyl matrix. as thin as only 20 molecular layers, about half of the embedded emitters withstand photobleaching for illumination times of at least a day. (C) 2004 Elsevier B.V. All rights reserved.

Near-field optical investigations of photonic crystal microresonators

B.C. Buchler, P. Kramper, M. Kafesaki, C.M. Soukoulis, Vahid Sandoghdar

IEICE Transactions on Electronics E87C 371-377 (2004)

We present an overview of our work on the application of scanning near-field optical microscopy (SNOM) to photonic crystal structures. Our results show that SNOM can be used to map the subwavelength confinement of light to a point-defect in a 2D photonic crystal microresonator. Comparison with numerical modelling shows that SNOM is able to resolve patterns in the intensity distribution that are due to the slight non-uniformity in the crystal structure. We also discuss the future possibilities for applications of different modes of SNOM to photonic crystal devices.

Detection and spectroscopy of gold nanoparticles using supercontinuum white light confocal microscopy

Klas Lindfors, Thomas Kalkbrenner, Patrick Stoller, Vahid Sandoghdar

Physical Review Letters 93 037401 (2004) | Journal

We combine confocal microscopy using supercontinuum laser illumination and an interferometric detection technique to identify single nanoparticles of diameter below 10 nm. Spectral analysis of the signal allows us to record the plasmon resonance of a single nanoparticle. Our results hold great promise for fundamental studies of the optical properties of single metal clusters and for their use in biophysical applications.

Confocal microscopy and spectroscopy of nanocrystals on a high-Q microsphere resonator

Stephan Götzinger, L. de S. Menezes, O. Benson, D.V. Talapin, N. Gaponik, H. Weller, A.L. Rogach, Vahid Sandoghdar

Journal of Optics B: Quantum and Semiclassical Optics 6 154-158 (2004) | Journal

We report on experiments where we used a home-made confocal microscope to excite single nanocrystals on a high-Q microsphere resonator. In that way spectra of an individual quantum emitter could be recorded. The Q factor of the microspheres coated with nanocrystals was still up to 10(9). We also demonstrate the use of a prism coupler as a well-defined output port to collect the fluorescence of an ensemble of nanocrystals coupled to whispering-gallery modes.

Near-field visualization of light confinement in a photonic crystal microresonator

Patrcik Kramper, Maria Kafesaki, Costas M. Soukoulis, Albert Birner, Frank Muller, Ulrich Goesele, Ralf B. Wehrspohn, Jürgen Mlynek, Vahid Sandoghdar

Optics Letters 29 174-176 (2004) | Journal

By using scanning near-field optical microscopy, we directly map the subwavelength confinement of light around a point defect in a two-dimensional photonic crystal microresonator. Comparison of our results with the outcome of three-dimensional finite-difference time domain calculations allows us to identify small imperfections in the structure that result in the spatial modification of the intensity distribution. (C) 2004 Optical Society of America

Highly directional emission from photonic crystal waveguides of subwavelength width

P. Kramper, M. Agio, C.M. Soukoulis, A. Birner, F. Muller, R.B. Wehrspohn, U. Goesele, Vahid Sandoghdar

Physical Review Letters 92 113903 (2004) | Journal

Recently it has been shown that it is possible to achieve directional emission out of a subwavelength aperture in a periodically corrugated metallic thin film. We report on theoretical and experimental studies of a related phenomenon concerning light emitted from photonic crystal waveguides that are less than a wavelength wide. We find that the termination of the photonic crystal end facets and an appropriate choice of the wavelength are instrumental in achieving very low numerical apertures. Our results hold promise for the combination of photonic crystal waveguides with conventional optical systems such as fibers, waveguides, and freely propagating light beams.

Subwavelength emitters in the near-infrared based on mercury telluride nanocrystals

P. Olk, B.C. Buchler, Vahid Sandoghdar, N. Gaponik, A. Eychmuller, A.L. Rogach

Applied Physics Letters 84 4732-4734 (2004) | Journal

The optical properties of near-infrared-emitting mercury telluride (HgTe) nanocrystals are investigated using fluorescence confocal microscopy. The HgTe quantum dots were coated with a "layer-by-layer" process on latex spheres with diameters down to 150 nm and number of layers varying from 1 to 3. The individual spheres act as bright subwavelength light sources. Measurements of the fluorescence decay show that the lifetime varies with the number of nanocrystal layers. (C) 2004 American Institute of Physics.

Born on April 29, 1966 in Tehran, Iran. Bachelor of Science in Physics from the University of California in Davis (1987), Ph.D. in Physics (supervisors: E. A. Hinds and S. Haroche) from Yale University (1993), Postdoctoral Fellow at École Normale Supérieure (group of S. Haroche) in Paris. Head of the Nano-Optics group und habilitation in Physics at University of Konstanz (Chair of J. Mlynek). Professorship at Eidgenössischen Technischen Hochschule (ETH) Zurich (2001-2011). Recipient of an ERC Advanced Grant (2010). Alexander von Humboldt Professorship at Friedrich-Alexander-Universität Erlangen-Nürnberg and Director and Scientific Member at the Max Planck Institute for the Science of Light in Erlangen since 2011. Fellow of the Optical Society (OSA) and recepient of the 2023 Quantum Electronics and Optics Award for Fundamental Aspects from the European Physical Society. Founder of the Max-Planck-Zentrum für Physik und Medizin, a joint research center that aims to address questions in fundamental medical research with physical and mathematical methods.

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