Optimizing spin polarization in quantum dot vertical-gain structures through pump wavelength selection

TL;DR

This study investigates how pump wavelength selection influences spin polarization in InAs quantum dots within vertical-cavity gain structures, revealing optimal excitation conditions for maximizing spin polarization relevant to telecom laser applications.

Contribution

It demonstrates the dependence of spin polarization on pump wavelength and identifies the optimal wavelength for maximum polarization in quantum dot structures.

Findings

Maximum spin polarization of nearly 5% at 980 nm pump wavelength

Spin polarization strongly depends on pump wavelength

Effective spin lifetime estimated at 40 ps

Abstract

Spintronic applications require an efficient injection of spin-polarized carriers. We study the maximally achievable spin polarization in InAs quantum dots in a vertical-cavity gain structure to be used in telecoms-wavelength vertical-external-cavity surface-emitting lasers via measurement of the Stokes parameter of the photoluminescence emission around 1290 nm. Using five pump wavelengths between 850 and 1070 nm, the observed spin polarization depends strongly on the pump wavelength with the highest polarization of nearly 5% found for excitation at 980 nm. This corresponds to an effective spin lifetime of 40 ps and is attributed to the dominant excitation of heavy holes only.