Abstract

Under spatially non-uniform photoexcitation of photrorefractive crystal, a diffusive transport of high mobility carriers (electrons) builds-up a space charge field (SC) which later affects the spatial distribution both of electrons and holes. Recent studies on free carrier (FC), photorefractive (PR), and absorptive nonlinearities in GaAs:EL2 and CdTe:V [1,2] revealed variety of effects related to the room-temperature EL2 defect metastability and defect-association assisted carrier generation. The further numerical analysis of the nonequiligrium free carrier dynamics in SC field has shown that spatio-temporal evolution of electron and hole gratings may cause a “dip” in FC optical nonlinearity as shown in Fig. 1. From the other hand, the similar effect may take place in PR grating dynamics as well, if an origin of the SC field varies with time: e.g. if SC field between electrons and ionized deep traps is replaced by a hole-governed SC field, after the electrons are captured by fast recombination centers.

© 2000 IEEE