Tracking Dark Excitons with Exciton Polaritons in Semiconductor Microcavities

TL;DR

This paper demonstrates the detection and characterization of dark excitons in semiconductor microcavities using exciton polaritons, revealing their long lifetime and potential for optical memory applications.

Contribution

It introduces a novel method to observe dark excitons via their interaction with bright polaritons, and provides a quantitative rate equation model for their dynamics.

Findings

Dark excitons have a lifetime exceeding 20 ns.

A memory effect is observed due to long-lived dark excitons.

The rate equation model accurately describes exciton-polariton interactions.

Abstract

Dark excitons are of fundamental importance for a wide variety of processes in semiconductors, but are difficult to investigate using optical techniques due to their weak interaction with light fields. We reveal and characterize dark excitons injected by non-resonant pulsed excitation in a semiconductor microcavity structure containing InGaAs/GaAs quantum wells by monitoring their interactions with the bright lower polariton mode. We find a surprisingly long dark exciton lifetime of more than 20 ns which is longer than the time delay between two consecutive pulses. This creates a memory effect that we clearly observe through the variation of the time-resolved transmission signal. We propose a rate equation model that provides a quantitative agreement with the experimental data.