Polarization properties of excitonic qu-bits in single self-assembled quantum dots

TL;DR

This study explores the polarization characteristics of neutral exciton emissions in single InAs/GaAs quantum dots, revealing how shape, strain anisotropy, and valence band mixing influence optical anisotropy and polarization axes.

Contribution

It provides new insights into the polarization behavior of excitons in quantum dots, highlighting the role of shape, strain, and valence band mixing in optical anisotropy.

Findings

Large optical anisotropy with non-orthogonal polarization states

Detection of luminescence polarization along the growth axis

Valence band mixing affects oscillator strength ratios

Abstract

We investigate polarization properties of neutral exciton emission in single self-assembled InAs/GaAs quantum dots. The in-plane shape and strain anisotropy strongly couple the heavy and light hole states and lead to large optical anisotropy with non-orthogonal linearly polarized states misaligned with respect to the crystallographic axes. Owing to a waveguiding experimental configuration, luminescence polarization along the growth axis has been observed revealing the presence of shear components of the deformation tensor out of the growth plane. Resonant luminescence experiments allowed determining the oscillator strength ratio of the two exciton eigenstates. Valence band mixing governs this ratio and can be very different from dot to dot, however the polarization anisotropy axis is quite fixed inside a scanned area of one \mum^{2} and indicates that the in-plane deformation direction to which it is related has a correlation length of the order of magnitude of one \mum^{2}.