Accurate measurement of a 96% input coupling into a cavity using polarization tomography

TL;DR

This paper introduces a polarization tomography technique to precisely measure input and output coupling efficiencies in pillar microcavities, achieving a 96% input coupling measurement with high accuracy, crucial for quantum network development.

Contribution

The paper presents a novel polarization tomography method leveraging residual birefringence to accurately distinguish coupled and uncoupled light in microcavities.

Findings

Measured 96% input coupling efficiency with high precision.

Achieved 53% output coupling efficiency measurement.

Demonstrated the technique's effectiveness for microcavity characterization.

Abstract

Pillar microcavities are excellent light-matter interfaces providing an electromagnetic confinement in small mode volumes with high quality factors. They also allow the efficient injection and extraction of photons, into and from the cavity, with potentially near-unity input and output-coupling efficiencies. Optimizing the input and output coupling is essential, in particular, in the development of solid-state quantum networks where artificial atoms are manipulated with single incoming photons. Here we propose a technique to accurately measure input and output coupling efficiencies using polarization tomography of the light reflected by the cavity. We use the residual birefringence of pillar microcavities to distinguish the light coupled to the cavity from the uncoupled light: the former participates to rotating the polarization of the reflected beam, while the latter decreases the polarization purity. Applying this technique to a micropillar cavity, we measure a $53 \pm2 \% $ output coupling and a $96 \pm 1\%$ input coupling with unprecedented precision.