HOT-CARRIER-TRANSPORT-GOVERNED NONRESONANT OPTICAL NONLINEARITY - TRANSIENT GUNN-DOMAIN GRATING

We review recent investigations of nonlinear carrier transport and rel ated optical nonlinearities in GaAs and InP crystals for the case in w hich photoexcited carriers are nonuniformly heated by a strong externa l electric field and are redistributed in a spatially nonuniform inter nal electric field. We simulated the nonequilibrium carrier and intern al field spatial evolution in picosecond and nanosecond time domains a nd estimated criteria for bipolar high-field Gunn-domain grating forma tion in de and ac fields. The coexisting refractive-index modulation m echanisms for free-carrier and electro-optic nonlinearities are analyz ed for various external field strengths, grating periods, and excitati on levels, thus providing conditions for an efficient and fast electro -optic refractive-index modulation by the transient Gunn-domain gratin g. Comparison of the experimentally observed enhancement of light's se lf-diffraction efficiency with numerical calculations has confirmed th at the nonresonant electro-optic Gunn-domain-based nonlinearity may ex ceed the free-carrier nonlinearity. (C) 1998 Optical Society of Americ a.