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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.

2005

Measuring the quantum efficiency of the optical emission of single radiating dipoles using a scanning mirror

B.C. Buchler, Thomas Kalkbrenner, C. Hettich, Vahid Sandoghdar

Physical Review Letters 95 063003 (2005) | Journal

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.

Spontaneous emission in the near field of two-dimensional photonic crystals

A. Femius Koenderink, Maria Kafesaki, Costas M. Soukoulis, Vahid Sandoghdar

Optics Letters 30 3210-3212 (2005) | Journal

We show theoretically that photonic crystal membranes cause large variations in the spontaneous emission rate of dipole emitters, not only inside but also in the near field above the membranes. Our three-dimensional finite-difference time-domain calculations reveal an inhibition of more than five times and an enhancement of more than ten times for the spontaneous emission rate of emitters with select dipole orientations and frequencies. Furthermore, we demonstrate theoretically the potential of a nanoscopic emitter attached to the end of a glass fiber tip as a local probe for mapping the large spatial variations of the photonic crystal local radiative density of states. This arrangement is promising for on-command modification of the coupling between an emitter and the photonic crystal in quantum optical experiments. (c) 2005 Optical Society of America.

Optical microscopy via spectral modifications of a nanoantenna

Thomas Kalkbrenner, Ulf Hakanson, A. Schadle, S. Burger, C. Henkel, Vahid Sandoghdar

Physical Review Letters 95 200801 (2005) | Journal

The existing optical microscopes form an image by collecting photons emitted from an object. Here we report on the experimental realization of microscopy without the need for direct optical communication with the sample. To achieve this, we have scanned a single gold nanoparticle acting as a nanoantenna in the near field of a sample and have studied the modification of its intrinsic radiative properties by monitoring its plasmon spectrum.

Controlling the resonance of a photonic crystal microcavity by a near-field probe

A. Femius Koenderink, Maria Kafesaki, Ben C. Buchler, Vahid Sandoghdar

Physical Review Letters 95 153904 (2005) | Journal

We demonstrate theoretically that the resonance frequencies of high-Q microcavities in two-dimensional photonic crystal membranes can be tuned over a wide range by introducing a subwavelength dielectric tip into the cavity mode. Three-dimensional finite-difference time-domain simulations show that by varying the lateral and vertical positions of the tip, it is possible to tune the resonator frequency without lowering the quality factor. Excellent agreement with a perturbative theory is obtained, showing that the tuning range is limited by the ratio of the cavity mode volume to the effective polarizability of the nanoperturber.

Optimization of prism coupling to high-Q modes in a microsphere resonator using a near-field probe

A. Mazzei, Stephan Götzinger, L. de S. Menezes, Vahid Sandoghdar, O. Benson

Optics Communications 250 428-433 (2005) | Journal

In this paper, we demonstrate a novel method for optimizing the in- and out-coupling of light confined in the fundamental high-Q whispering-gallery mode of a microsphere resonator via an external prism coupler. The technique relies on the use of a near-field probe to map the modes of the resonator and to obtain topographical information at the same time. We demonstrate the feasibility and efficiency of this technique by applying it to a sphere with a radius of 59 mu m. (c) 2005 Elsevier B.V. All rights reserved.

Near-field optics and control of photonic crystals

A. Femius Koenderink, R. Wuest, Ben C. Buchler, S. Richter, P. Strasser, Maria Kafesaki, A. Rogach, R.B. Wehrspohn, C.M. Soukoulis, et al.

Photonics and Nanostructures - Fundamentals and Applications 3 63-74 (2005) | Journal

We discuss recent progress and the exciting potential of scanning probe microscopy methods for the characterization and control of photonic crystals. We demonstrate that scanning near-field optical microscopy can be used to characterize the performance of photonic crystal device components on the sub-wavelength scale. In addition, we propose scanning probe techniques for realizing local, low-loss tuning of photonic crystal resonances, based on the frequency shifts that high-index nanoscopic probes can induce. Finally, we discuss prospects for on-demand spontaneous emission control. We demonstrate theoretically that photonic crystal membranes induce large variations in spontaneous emission rate over length scales of 50 nm that can be probed by single light sources, or nanoscopic ensembles of light sources attached to the end of a scanning probe. (c) 2005 Elsevier B.V. All rights reserved.

A "standing-wave meter" to measure dispersion and loss of photonic-crystal waveguides

R. Wuest, D. Erni, P. Strasser, F. Robin, H. Jackel, B.C. Buchler, A.F. Koenderink, Vahid Sandoghdar, R. Harbers

Applied Physics Letters 87 261110 (2005) | Journal

We demonstrate a "standing-wave meter" for measuring dispersion and loss along the length of a planar InP-based photonic-crystal waveguide. Light from a tunable cw laser was coupled into a single line-defect waveguide that terminated inside the crystal structure to form a retroreflector. This structure created a standing wave which was imaged using a scanning near-field optical microscope. By measuring the intensity distribution of the standing wave for a range of optical frequencies, waveguide dispersion and loss were measured with high accuracy. Comparisons of the measurement results with three-dimensional numerical simulations reveal that material dispersion effects as small as 0.8% affect the band structure measurably. (c) 2005 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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