Abstract

Spin controlled vertical cavity surface emitting lasers (VCSELs) have several beneficial features, such as threshold reduction and circularly polarized lasing. We previously demonstrated 1 GHz switching between lasing circular polarizations with two opposite directions in a VCSEL based on a (110) oriented multiple quantum well (MQW) with a degree of circular polarization higher than 0.9 [1]. Shortening the carrier lifetime τ_c while preserving the electron spin relaxation time τ_s is a straightforward solution to switching the lasing circular polarizations faster since residual electrons in the MQW deteriorate the degree of spin polarization. We therefore introduced micropost structures in a (110) MQW. However, we could not measure τ_s in microposts smaller than 2 μm due to the time resolution of the streak camera (~25 ps) [2]. Although use of the microposts with a fast non radiative surface recombination is a promising approach for faster polarization switching in spin controlled VCSELs, it is still unclear if τs in useful post sizes smaller than 2 μm can be kept long. In this work, we measured τ_c and τ_s in (110) GaAs/AlGaAs MQW microposts with special attention to those smaller than 2 μm using a pump probe based time resolved Kerr rotation (TRKR) technique. We also report the results of rate equation analysis in a micropost VCSEL using the measured τ_c and τ_s.

© 2013 IEEE