Femtosecond Orientational Relaxation of Photoexcited Carriers in GaAs

Abstract

The anisotropy of optical absorption saturation by intense linearly polarized light pulses is measured with subpicosecond resolution in GaAs at 77 K, at a photon energy slightly above the band gap. For an electron-hole pair density of about 6\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, the momentum orientational relaxation time is determined to be 190 fs, most likely due to carrier-carrier scattering.