Mode Interference Effect in Optical Emission of Quantum Dots in Photonic Crystal Cavities

Radiation properties of a pointlike source of light, such as a molecule or a semiconductor quantum dot, can be tailored by modifying its photonic environment. This phenomenon lies at the core of cavity quantum electrodynamics (CQED). Quantum dots in photonic crystal microcavities have served as a model system for exploring the CQED effects and for the realization of efficient single-photon quantum emitters. Recently, it has been suggested that quantum interference of the exciton recombination paths through the cavity and free-space modes can significantly modify the radiation. In this work, we report an unambiguous experimental observation of this fundamental effect in the emission spectra of site-controlled quantum dots positioned at prescribed locations within a photonic crystal cavity. The observed asymmetry in the polarization-resolved emission spectra strongly depends on the quantum dot position, which is confirmed by both analytical and numerical calculations. We perform quantum interferometry in the near-field zone of the radiation, retrieving the overlap and the position-dependent relative phase between the interfering freespace and cavity-mode-mediated radiative decays. The observed phenomenon is of importance for realization of photonic-crystal light emitters with near unity quantum efficiency. Our results suggest that the full description of light-matter interaction in the framework of CQED requires a modification of the conventional quantum master equation by also considering the radiation mode interference.

Automated summary

The radiation properties of pointlike sources like molecules or semiconductor quantum dots can be modified by changing the surrounding photonic environment, which is a core concept in cavity quantum electrodynamics (CQED). Quantum dots in photonic crystal microcavities have been used as a model system to study these effects and for creating efficient single-photon quantum emitters. Recent research has shown that quantum interference of exciton recombination paths through cavity and free-space modes can change the radiation significantly. This study reports experimental evidence of this effect in the emission spectra of quantum dots placed in specific locations within a photonic crystal cavity, showing asymmetry in the polarization-resolved emission spectra depending on the quantum dot position.