Moving space-charge field effects in photoconductive semiconductors with interband optical excitation of free charge carriers

An internal space-charge electric field is established when two mutually coherent optical fields interfere inside an intrinsic photoconductive semiconductor containing deep-level recombination centers with band-gap energy smaller than the incident photon energy. Dc photocurrents are generated when the two optical fields have unequal center frequencies. A mathematical characterization of the behavior of the do photocurrent, which can be used to characterize the host photoconductive material, is presented and verified experimentally for a Si sample. (C) 1997 Optical Society of America.