Tuning of the Electron Spin Relaxation Anisotropy via Optical Gating in GaAs/AlGaAs Quantum Wells

The carrier-density-dependent spin relaxation dynamics for modulation-doped GaAs/Al_0.3Ga_0.7As quantum wells is studied using the time-resolved magneto-Kerr rotation measurements. The electron spin relaxation time and its in-plane anisotropy are studied as a function of the optically injected electron density. Moreover, the relative strength of the Rashba and the Dresselhaus spin–orbit coupling fields, and thus the observed spin relaxation time anisotropy, is further tuned by the additional excitation of a 532 nm continuous wave laser, demonstrating an effective spin relaxation manipulation via an optical gating method.