Evanescent-field assisted photon collection from quantum emitters under a solid immersion lens

TL;DR

This study demonstrates that an index-matched solid immersion lens can significantly enhance photon collection efficiency from quantum emitters in high refractive index materials by exploiting evanescent fields, with experimental and numerical validation.

Contribution

It introduces a method using a solid immersion lens to improve photon extraction from quantum emitters, highlighting the importance of spacer thickness for efficiency enhancement.

Findings

Mean photon collection efficiency enhancement factor of 4.2

Maximum photon detection rate of 743 kcps

Spacer thickness critically affects collection efficiency

Abstract

Solid-state quantum light sources are being intensively investigated for applications in quantum technology. A key challenge is to extract light from host materials with high refractive index, where efficiency is limited by refraction and total internal reflection. Here we show that an index-matched solid immersion lens can, if placed sufficiently close to the semiconductor, extract light coupled through the evanescent field at the surface. Using both numerical simulations and experiments, we investigate how changing the thickness of the spacer between the semiconductor and lens impacts the collection efficiency (CE). Using automatic selection and measurement of 100 s of individually addressable colour centres in several aluminium nitride samples we demonstrate spacer-thickness dependent photon CE enhancement, with a mean enhancement factor of 4.2 and a highest measured photon detection rate of 743 kcps.