Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission

TL;DR

This paper introduces a nanoscale optical positioning technique for single quantum dots that enables the fabrication of highly efficient, pure single-photon sources with precise control over quantum dot placement.

Contribution

The authors develop a photoluminescence imaging method achieving sub-30 nm accuracy for locating quantum dots, facilitating optimized device fabrication.

Findings

Position uncertainty < 30 nm, < 10 nm with solid immersion lens

Quantum dot single-photon sources with 48% collection efficiency

Low multiphoton probability (<1%) and Purcell factor ~3

Abstract

Self-assembled, epitaxially-grown InAs/GaAs quantum dots are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of quantum dots, presenting a challenge in creating devices that exploit the strong interaction of single quantum dots with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single quantum dots with respect to alignment features with an average position uncertainty < 30 nm (< 10 nm when using a solid immersion lens), which represents an enabling technology for the creation of optimized single quantum dot devices. To that end, we create quantum dot single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48 % +/- 5 % into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50 %), low multiphoton probability (g(2)(0) <1 %), and a significant Purcell enhancement factor (~ 3).