Optical two-photon absorption in GaAs measured by optical pump-terahertz probe spectroscopy

Abstract

A novel scheme of optical pump-THz probe experiments was used to study the nonlinear absorption in GaAs. The crystal was excited by ultrashort laser pulses with wavelength 810 nm and fluences up to 4.2 mJ/cm/sup 2/, for which the single-photon absorption (SPA) saturates and the two-photon absorption (TPA) dominates. The TPA coefficient /spl beta/ and its anisotropy were determined.