Subpicosecond spin relaxation in GaAsSb multiple quantum wells

Spin relaxation times in GaAsxSb1-x quantum wells are measured at 295 K usi ng time-resolved circular dichroism induced by 1.5 mu m, 100 fs pulses. Val ues of 1.03 and 0.84 ps are obtained for samples with x = 0 and 0.188, resp ectively. These times are > 5 times shorter than those in InGaAs and InGaAs P wells with similar band gaps. The shorter relaxation times are attributed to the larger spin-orbit conduction-band splitting in the Ga(As)Sb system, consistent with the D'yakonov-Perel theory of spin relaxation [M. I. D'yak onov and V. I. Perel, Sov. Phys. JETP 38, 177 (1974)]. Our results indicate the feasibility of engineering an all-optical, polarization switch at 1.5 mu m with response time < 250 fs. (C) 1999 American Institute of Physics. [ S0003-6951(99)02549-8].