All-Optical Depletion of Dark Excitons from a Semiconductor Quantum Dot

TL;DR

This paper presents an all-optical method to deplete dark excitons in semiconductor quantum dots, significantly improving single-photon source efficiency by converting dark to bright excitons using intermediate biexciton states.

Contribution

The authors introduce a novel optical pumping technique that effectively reduces dark excitons and enhances bright exciton emission in quantum dots, nearing near-unit depletion fidelity.

Findings

Dark exciton population is significantly reduced.

Bright exciton emission is doubled.

Depletion fidelity approaches near unity.

Abstract

Semiconductor quantum dots are considered to be the leading venue for fabricating on-demand sources of single photons. However, the generation of long-lived dark excitons imposes significant limits on the efficiency of these sources. We demonstrate a technique that optically pumps the dark exciton population and converts it to a bright exciton population, using intermediate excited biexciton states. We show experimentally that our method considerably reduces the DE population while doubling the triggered bright exciton emission, approaching thereby near-unit fidelity of quantum dot depletion.