Spectroscopy of coupled optical microcavities with quantum emitters

Violetta Sharoglazova, Marius Puplauskis, Carl Ulrich Mattschas +3 more

Raphael Gutbrod, Alexey I. Chizhik, Anna M. Chizhik +4 more

Optical microcavities are structures which confine light to a small region in the range of one wavelength. The radiation of a quantum emitter is coupled to cavity resonances which leads to an optical confinement of the broadband fluorescence. A practical design for this single-mode microcavity is formed by two silver mirrors enclosing a transparent dielectric medium with single quantum emitters. Steiner et al. have shown that the fluorescence spectra and decay lifetimes of single molecules in this Fabry-Perot type microcavity are strongly dependent on the resonator length.

Ravyn Malatesta, Lorenzo Uboldi, Evan J. Kumar +6 more

Optical microcavities are often proposed as platforms for spectroscopy in the single- and few-photon regime due to strong light-matter coupling. For classical-light spectroscopies, an empty microcavity simply acts as an optical filter. However, we find that in the single- or few-photon regime treating the empty microcavity as an optical filter does not capture the full effect on the quantum state of the transmitted photons. Focusing on the case of entangled photon-pair spectroscopy, we consider how the propagation of one photon through an optical microcavity changes the joint spectrum of a frequency-entangled photon pair. Using the input-output treatment of a Dicke model, we find that propagation through a strongly coupled microcavity above a certain coupling threshold enhances the entanglement entropy between the signal and idler photons. These results show that optical microcavities are not neutral platforms for quantum-light spectroscopies and their effects must be carefully considered when using change in entanglement entropy as an observable.

Matthew T. Rakher

Yang Yu, Chunran Li, Yanan Yu +4 more

High-performance single-photon sources (SPSs) are essential components for quantum information technology and have been realized by strong coupling between a single quantum emitter and an optical cavity. However, the configurations of conventional SPSs are not ideal for long-distance quantum communication as they are intrinsically incompatible with optical fibers. Here we propose and design a strong-coupling system based on a single quantum emitter directly coupled with an in-fiber microcavity. The in-fiber microcavity not only achieves a high coupling efficiency of 83% and a high Purcell factor of 360, but also pushes the coupling system to enter the strong-coupling region with a vacuum Rabi splitting up to 4.35 meV. This enables a high quantum efficiency of 99% for a SPS. Our work presents a promising platform for realizing high-performance SPSs for long-distance quantum communication.