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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.

2021

Optimized analysis for sensitive detection and analysis of single proteins via interferometric scattering microscopy

Houman Mirzaalian Dastjerdi, Mahyar Dahmardeh, André Gemeinhardt, Reza Gholami Mahmoodabadi, Harald Köstler, Vahid Sandoghdar

Journal of Physics D: Applied Physics 55 054002 (2021) | Journal

It has been shown that interferometric detection of Rayleigh scattering (iSCAT) can reach an exquisite sensitivity for label-free detection of nano-matter, down to single proteins. The sensitivity of iSCAT detection is intrinsically limited by shot noise, which can be indefinitely improved by employing higher illumination power or longer integration times. In practice, however, a large speckle-like background and technical issues in the experimental setup limit the attainable signal-to-noise ratio. Strategies and algorithms in data analysis are, thus, crucial for extracting quantitative results from weak signals, e.g. regarding the mass (size) of the detected nano-objects or their positions. In this article, we elaborate on some algorithms for processing iSCAT data and identify some key technical as well as conceptual issues that have to be considered when recording and interpreting the data. The discussed methods and analyses are made available in the extensive python-based platform, PiSCAT.

Single-molecule vacuum Rabi splitting: four-wave mixing and optical switching at the single-photon level

André Pscherer, Manuel Meierhofer, Daqing Wang, Hrishikesh Kelkar, Diego-Martin Cano, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar

Physical Review Letters 127 133603 (2021) | Journal

A single quantum emitter can possess a very strong intrinsic nonlinearity, but its overall promise for nonlinear effects is hampered by the challenge of efficient coupling to incident photons. Common nonlinear optical materials, on the other hand, are easy to couple to but are bulky, imposing a severe limitation on the miniaturization of photonic systems. In this work, we show that a single organic molecule acts as an extremely efficient nonlinear optical element in the strong coupling regime of cavity quantum electrodynamics. We report on single-photon sensitivity in nonlinear signal generation and all-optical switching. Our work promotes the use of molecules for applications such as integrated photonic circuits, operating at very low powers.

suggested by editors

Engineering long-lived vibrational states for an organic molecule

Burak Gürlek, Vahid Sandoghdar, Diego-Martin Cano

Physical Review Letters 127 123603 (2021) | Journal

The optomechanical character of molecules was discovered by Raman about one century ago. Today, molecules are promising contenders for high-performance quantum optomechanical platforms because their small size and large energy-level separations make them intrinsically robust against thermal agitations. Moreover, the precision and throughput of chemical synthesis can ensure a viable route to quantum technological applications. The challenge, however, is that the coupling of molecular vibrations to environmental phonons limits their coherence to picosecond time scales. Here, we improve the optomechanical quality of a molecule by several orders of magnitude through phononic engineering of its surrounding. By dressing a molecule with long-lived high-frequency phonon modes of its nanoscopic environment, we achieve storage and retrieval of photons at millisecond time scales and allow for the emergence of single-photon strong coupling in optomechanics. Our strategy can be extended to the realization of molecular optomechanical networks.

On Quantum Efficiency Measurements and Plasmonic Nano-Antennas

Korenobu Matsuzaki, Hsuan-Wei Liu, Stephan Götzinger, Vahid Sandoghdar

ACS Photonics 8 1508-1521 (2021) | Journal

Quantum efficiency is a key quantity that describes the performance of light-emitting materials and is, thus, an important metric for assessing novel nanophotonic systems. This Perspective provides a concise discussion of the difficulties encountered in the characterization of quantum efficiencies, especially for studies that involve single emitters. In particular, we review various approaches that have been recently used for determining quantum efficiencies of emitters coupled to plasmonic antennas and highlight the subtleties and challenges that hinder precise measurements.

Single organic molecules for photonic quantum technologies

C. Toninelli, I. Gerhardt, A.S. Clark, A. Reserbat-Plantey, Stephan Götzinger, Z. Ristanovic, M. Colautti, P. Lombardi, K.D. Major, et al.

Nature Materials 2021 (2021) | Journal

Isolating single molecules in the solid state has allowed fundamental experiments in basic and applied sciences. When cooled down to liquid helium temperature, certain molecules show transition lines, that are tens of megahertz wide, limited only by the excited state lifetime. The extreme flexibility in the synthesis of organic materials provides, at low costs, a wide palette of emission wavelengths and supporting matrices for such single chromophores. In the last decades, the controlled coupling to photonic structures has led to an optimized interaction efficiency with light. Molecules can hence be operated as single photon sources and as non-linear elements with competitive performance in terms of coherence, scalability and compatibility with diverse integrated platforms. Moreover, they can be used as transducers for the optical read-out of fields and material properties, with the promise of single-quanta resolution in the sensing of charges and motion. We show that quantum emitters based on single molecules hold promise to play a key role in the development of quantum science and technologies.

Nanoscopic charge fluctuations in a gallium phosphide waveguide measured by single molecules

Alexey Shkarin, Dominik Rattenbacher, Jan Renger, Simon Hönl, Tobias Utikal, Paul Seidler, Stephan Götzinger, Vahid Sandoghdar

Physical Review Letters 126 133602 (2021) | Journal

We present efficient coupling of single organic molecules to a gallium phosphide subwavelengthwaveguide (nanoguide). By examining and correlating the temporal dynamics of various single-molecule resonances at different locations along the nanoguide, we reveal light-induced fluctuationsof their Stark shifts. Our observations are consistent with the predictions of a simple model basedon the optical activation of a small number of charges in the GaP nanostructure.

Precision single-particle localization using radial variance transform

Anna D. Kashkanova, Alexey Shkarin, Reza Gholami Mahmoodabadi, Martin Blessing, Yazgan Tuna, André Gemeinhardt, Vahid Sandoghdar

Optics Express 29 11070-11083 (2021) | Journal

We introduce an image transform designed to highlight features with high degree of radial symmetry for identification and subpixel localization of particles in microscopy images. The transform is based on analyzing pixel value variations in radial and angular directions. We compare the subpixel localization performance of this algorithm to other common methods based on radial or mirror symmetry (such as fast radial symmetry transform, orientation alignment transform, XCorr, and quadrant interpolation), using both synthetic and experimentally obtained data. We find that in all cases it achieves the same or lower localization error, frequently reaching the theoretical limit.

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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