My research is focused on solid-state quantum optics. In the past few years I have, for example, investigated methods to collect single photons with near-unity efficiency. Another emphasis is on techniques which can be used to enhance the interaction of a single photon with a single emitter.
Scanning probe microscopes scan and manipulate a sharp tip in the immediate vicinity of a sample surface. The limited bandwidth of the feedback mechanism used for stabilizing the separation between the tip and the sample makes the fragile nanoscopic tip very susceptible to mechanical instabilities. We propose, demonstrate, and characterize an alternative device based on bulging a thin substrate against a second substrate and rolling them with respect to each other. We showcase the power of this method by placing gold nanoparticles and semiconductor quantum dots on the two opposite substrates and positioning them with nanometer precision to enhance the fluorescence intensity and emission rate. Furthermore, we exhibit the passive mechanical stability of the system over more than 1 h. Our design concept finds applications in a variety of other scientific and technological contexts, where nanoscopic features have to be positioned and kept near contact with each other. a thin substrate against a second substrate and rolling them with respect each other. We showcase the power of this method by placing gold nanoparticles and semiconductor quantum dots on the two opposite substrates and positioning them with nanometer precision to enhance the fluorescence intensity and emission rate. We exhibit the passive mechanical stability of the system over more than one hour. The design concept presented in this work holds promise in a variety of other contexts, where nanoscopic features have to be positioned and kept near contact with each other.
High-resolution vibronic spectroscopy of a single molecule embedded in a
crystal
Johannes Zirkelbach,
Masoud Mirzaei,
Irena Deperasińska,
Boleslaw Kozankiewicz,
Burak Gürlek,
Alexey Shkarin,
Tobias Utikal,
Stephan Götzinger,
Vahid Sandoghdar
The Journal of Chemical Physics
156
104301
(2022)
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Vibrational levels of the electronic ground states in dye molecules have not been previously explored at a high resolution in solid matrices. We present new spectroscopic measurements on single polycyclic aromatic molecules of dibenzoterrylene embedded in an organic crystal made of para-dichlorobenzene. To do this, we use narrow-band continuous-wave lasers and combine spectroscopy methods based on fluorescence excitation and stimulated emission depletion to assess individual vibrational linewidths in the electronic ground state at a resolution of ∼30 MHz dictated by the linewidth of the electronic excited state. In this fashion, we identify several exceptionally narrow vibronic levels with linewidths down to values around 2 GHz. Additionally, we sample the distribution of vibronic wavenumbers, relaxation rates, and Franck–Condon factors, in both the electronic ground and excited states for a handful of individual molecules. We discuss various noteworthy experimental findings and compare them with the outcome of density functional theory calculations. The highly detailed vibronic spectra obtained in our work pave the way for studying the nanoscopic local environment of single molecules. The approach also provides an improved understanding of the vibrational relaxation mechanisms in the electronic ground state, which may help create long-lived vibrational states for applications in quantum technology.
Single photon sources for quantum radiometry: a brief review about the current state‑of‑the‑art
Stefan Kück,
Marco López,
Helmuth Hofer,
Hristina Georgieva,
Justus Christinck,
Beatrice Rodiek,
Geiland Porrovecchio,
Marek Smid,
Stephan Götzinger, et al.
Applied Physics B: Lasers and Optics
128
28
(2022)
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Single-photon sources have a variety of applications. One of these is quantum radiometry, which is reported on in this paper in the form of an overview, specifically of the current state of the art in the application of deterministic single photon sources to the calibration of single photon detectors. To optimize single-photon sources for this purpose, extensive research is currently carried out at the European National Metrology Institutes (NMIs), in collaboration with partners from universities. Single-photon sources of different types are currently under investigation, including sources based on defect centres in (nano-)diamonds, on molecules and on semiconductor quantum dots. We will present, summarise, and compare the current results obtained at European NMIs for single-photon sources in terms of photon flux, single-photon purity, and spectral power distribution as well as the results of single-photon detector calibrations carried out with this type of light sources.
Comparison of back focal plane imaging of nitrogen vacancy centers in nanodiamond and core-shell CdSe/CdS quantum dots
Justus Christinck,
Beatrice Rodiek,
Marco Lopez,
Hristina Georgieva,
Stephan Götzinger,
Stefan Kück
Journal of Physics: Conference Series
2149
012014
(2022)
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We report on the characterization of the angular-dependent emission of two different single-photon emitters based on nitrogen-vacancy centers in nanodiamond and on core-shell CdSe/CdS quantum dot nanoparticles. The emitters were characterized in a confocal microscope setup by spectroscopy and Hanbury-Brown and Twiss interferometry. The angular-dependent emission is measured using a back focal plane imaging technique. A theoretical model of the angular emission patterns of the 2D dipoles of the emitters is developed to determine their orientation. Experiment and model agree well with each other.
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