Optical orientation of electron spins in GaAs L-valleys

We report on optical orientation experiments in GaAs epilayers with excitation energies in the 3 eV region, leading the photo-generation of spin-polarized electrons in the satellite L valley. From both continuous-wave and time resolved measurements we show that a significant fraction of the electron spin memory can be conserved when the electron is scattered from the L to the Γ valley following an energy relaxation of several hundreds of meV. A typical L-valley electron spin relaxation time of 200 fs is deduced, in agreement with theoretical calculations.