Bright single photon emission from a quantum dot in a circular Bragg grating microcavity

TL;DR

This paper demonstrates bright, efficient single photon emission from quantum dots in circular Bragg grating microcavities, with high collection efficiency and controllable multi-photon probability, advancing quantum photonics applications.

Contribution

It introduces a microcavity design that enhances photon collection and suppresses multi-photon events, with experimental validation and simulation analysis.

Findings

Achieved up to 10% collection efficiency.

Observed Purcell enhancement of ~10x.

Resonant excitation suppresses multi-photon probability.

Abstract

Bright single photon emission from single quantum dots in suspended circular Bragg grating microcavities is demonstrated. This geometry has been designed to achieve efficient (> 50 %) single photon extraction into a near-Gaussian shaped far-field pattern, modest (~10x) Purcell enhancement of the radiative rate, and a spectral bandwidth of a few nanometers. Measurements of fabricated devices show progress towards these goals, with collection efficiencies as high as ~10% demonstrated with moderate spectral bandwidth and rate enhancement. Photon correlation measurements are performed under above-bandgap excitation (pump wavelength = 780 nm to 820 nm) and confirm the single photon character of the collected emission. While the measured sources are all antibunched and dominantly composed of single photons, the multi-photon probability varies significantly. Devices exhibiting tradeoffs between collection efficiency, Purcell enhancement, and multi-photon probability are explored and the results are interpreted with the help of finite-difference time-domain simulations. Below-bandgap excitation resonant with higher states of the quantum dot and/or cavity (pump wavelength = 860 nm to 900 nm) shows a near-complete suppression of multi-photon events and may circumvent some of the aforementioned tradeoffs.