Spin precession and the optical Stark effect in a semiconductor-doped glass

Femtosecond-resolved pump-probe techniques are used to investigate spin-dependent phenomena in a semiconductor-doped glass at temperatures from 6 to 300 K and in magnetic fields from 0 to 2 T. Faraday rotation experiments reveal nanosecond-scale spin lifetimes at zero field that are decreased by an order of magnitude in a transverse field of 2 T. Differential transmission measurements are used to study the optical Stark shift of the absorption edge as the pump energy is tuned below the semiconductor band gap. A pronounced polarization dependence of the Stark shift is observed, yielding 3.8 meV (1.6 meV) shifts for co-polarized (cross-polarized) pump and probe beams. These experiments demonstrate a method of polarization-sensitive optical control in semiconductor nanostructures on {~}100-fs time scales.