My research focuses on the controlled coupling of individual organic dye molecules to photonic circuitry made from dielectric waveguides with subwavelength cross sections. The long-term goal of the project is to generate and investigate polaritonic states formed by several molecules coupled via the waveguide circuitry.
On-chip interference of scattering from two individual molecules in plastic
Dominik Rattenbacher, Alexey Shkarin, Jan Renger, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
Integrated photonic circuits offer a promising route for studying coherent cooperative effects of a controlled collection of quantum emitters. However, spectral inhomogeneities, decoherence and material incompatibilities in the solid state make this a nontrivial task. Here, we demonstrate efficient coupling of a pair of organic molecules embedded in a plastic film to a TiO2 microdisc resonator on a glass chip. Moreover, we tune the resonance frequencies of the molecules with respect to that of the microresonator by employing nanofabricated electrodes. For two molecules separated by a distance of about 8μm and an optical phase difference of about π/2, we report on a large collective extinction of the incident light in the forward direction and the destructive interference of its scattering in the backward direction. Our work sets the ground for the coherent coupling of several molecules via a common mode and the realization of polymer-based hybrid quantum photonic circuits.
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
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.
Coherent coupling of single molecules to on-chip ring resonators
Dominik Rattenbacher, Alexey Shkarin, Jan Renger, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
We report on cryogenic coupling of organic molecules to ring microresonators obtained by looping subwavelength waveguides (nanoguides). We discuss fabrication and characterization of the chip-based nanophotonic elements which yield a resonator finesse in the order of 20 when covered by molecular crystals. Our observed extinction dips from single molecules reach 22%, consistent with an expected enhancement factor of up to 11 for the molecular emission into the nanoguide. Future efforts will aim at efficient coupling of a handful of molecules via their interaction with a ring microresonator mode, setting the ground for the realization of quantum optical cooperative effects.
Turning a molecule into a coherent two-level quantum system
Daqing Wang, Hrishikesh Kelkar, Diego-Martin Cano, Dominik Rattenbacher, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
The use of molecules in quantum optical applications has been hampered by incoherent internal vibrations and other phononic interactions with their environment. Here we show that an organic molecule placed into an optical microcavity behaves as a coherent two-level quantum system. This allows the observation of 99% extinction of a laser beam by a single molecule, saturation with less than 0.5 photons and non-classical generation of few-photons super-bunched light. Furthermore, we demonstrate efficient interaction of the molecule–microcavity system with single photons generated by a second molecule in a distant laboratory. Our achievements represent an important step towards linear and nonlinear quantum photonic circuits based on organic platforms.
Dominik Rattenbacher studied physics in the "Physics Advanced Programme" at the Universities of Erlangen and Regensburg from 2013 to 2018. After a research stay at the Ultrafast and Attosecond Science group of Prof. Wörner at ETH Zurich, he started his Master thesis on "Spectroscopic investigation of two molecules coupled via a dielectric waveguide" at the MPL. The work of his PHD thesis is a direct continuation of this project and aims at coupling several molecules efficiently via a nanophotonic circuit.
