Abstract
Time-resolved terahertz experiments in a novel setup were used for a direct observation of the competition between the single- and two-photon absorption in highly excited GaAs. The experiments were carried out near where the single photon absorption usually dominates. The crystal surface was excited by femtosecond laser pulses with fluences up to , for which the single-photon absorption saturates and the two-photon absorption becomes the leading absorption mechanism. The two-photon absorption coefficient , its anisotropy and the depth profile of the photoexcited carriers were determined.
- Received 11 February 2004
DOI:https://doi.org/10.1103/PhysRevB.70.125205
©2004 American Physical Society