Exciton fine-structure splitting of telecom wavelength single quantum dots: statistics and external strain tuning

TL;DR

This study investigates how external uniaxial strain affects the fine-structure splitting of neutral excitons in long-wavelength InGaAs quantum dots, revealing varied responses and potential for tuning to generate entangled photon pairs at telecom wavelengths.

Contribution

It provides the first detailed statistical analysis of strain effects on telecom-wavelength quantum dots and introduces a phenomenological model to predict fine-structure tuning.

Findings

Fine structure splittings range from 16 to 136 μeV.

Splitting responses to strain vary widely, including positive, negative, linear, and parabolic behaviors.

Strain tuning can potentially cancel fine-structure splitting, enabling entangled photon generation.

Abstract

In a charge tunable device, we investigate the fine structure splitting of neutral excitons in single long-wavelength (1.1\mu m < \lambda < 1.3 \mu m) InGaAs quantum dots as a function of external uniaxial strain. Nominal fine structure splittings between 16 and 136 \mu eV are measured and manipulated. We observe varied response of the splitting to the external strain, including positive and negative tuning slopes, different tuning ranges, and linear and parabolic dependencies, indicating that these physical parameters depend strongly on the unique microscopic structure of the individual quantum dot. To better understand the experimental results, we apply a phenomenological model describing the exciton polarization and fine-structure splitting under uniaxial strain. The model predicts that, with an increased experimental strain tuning range, the fine-structure can be effectively canceled for select telecom wavelength dots using uniaxial strain. These results are promising for the generation of on-demand entangled photon pairs at telecom wavelengths.