Memory effect for polarization of pump light in optically pumped vertical-cavity semiconductor lasers

We report that the polarization of the emission of an optically pumped vertical-cavity surface-emitting laser (VCSEL) is sensitive to the polarization state of the pump light. By measuring this memory effect for circularly polarized pump light, we determine the normalized relaxation rate of the carrier spin, Γ_s, which is a vital parameter in current theoretical models of VCSEL polarization. We find Γ_s=300±150, a value which is significantly larger than previously estimated. We also observe a memory effect for the orientation of linearly polarized pump light. This signals that, apart from the carrier spin, the VCSEL polarization is also determined by the carrier momentum