Pump-probe second harmonic generation study of ultrafast spin dynamics in semiconductor multilayers

We report the first application of pump-probe second harmonic generation (SHG) measurements to characterize optically induced magnetization in non-magnetic multilayer semiconductors. In the experiment, spin-polarized electrons are excited selectively by a pump beam in the GaAs layer of GaAs/GaSb/InAs structures. However, the resulting net magnetization manifests itself through the induced SHG probe signal from the GaSb/InAs interface, thus indicating a spin-polarized electron transport across the heterostructure. We find that the magnetization dynamics are governed by an interplay between the spin density evolution at the interfaces and the spin relaxation. Copyright (C) 2003 John Wiley Sons, Ltd.