Optical injection and detection of ballistic pure spin currents in Ge

Ballistic pure spin currents are injected into Ge at 295 K using quantum interference between one and two photon absorption processes for 1786 and 893 nm, 200 fs optical pulses. The spin currents are spatially and temporally detected using polarization- and phase-dependent differential transmission techniques with nanometer spatial and femtosecond temporal resolution. We interpret the dynamics in terms of the fast spin relaxation of the holes and intervalley transfer of electrons. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3222869]