We review recent investigations of nonlinear carrier transport and related optical nonlinearities in GaAs and InP crystals for the case in which photoexcited carriers are nonuniformly heated by a strong external electric field and are redistributed in a spatially nonuniform internal electric field. We simulated the nonequilibrium carrier and internal field spatial evolution in picosecond and nanosecond time domains and estimated criteria for bipolar high-field Gunn-domain grating formation in dc and ac fields. The coexisting refractive-index modulation mechanisms for free-carrier and electro-optic nonlinearities are analyzed for various external field strengths, grating periods, and excitation levels, thus providing conditions for an efficient and fast electro-optic refractive-index modulation by the transient Gunn-domain grating. Comparison of the experimentally observed enhancement of light’s self-diffraction efficiency with numerical calculations has confirmed that the nonresonant electro-optic Gunn-domain-based nonlinearity may exceed the free-carrier nonlinearity.
[Optical Society of America ]
L. Subacius, E. Starikov, P. Shiktorov, V. Gruzinskis, and K. Jarasiunas, "Hot-carrier-transport-governed nonresonant optical nonlinearity: transient Gunn-domain grating," J. Opt. Soc. Am. B 15, 2045-2056 (1998)