Abstract

One of the most important parameters for the uses of photorefractive crystals is the speed of the photoinduced grating buildup. This time constant depends on the reduction state of the photoactive defects. One is primarily interested in a rapid redistribution of photoinduced charge carriers. This is the case in materials having a small concentration of trapping centers N_A, where the drift length $L_d={\Phi }_{\mu }{}_{T}E$ is large [comparable to the grating fringe spacing; μ, carrier mobility; $\tau ={\left({\gamma }_R{N}_A\right)}^{-1}$ carrier lifetime; ${\gamma }_R$, carrier recombination constant, E, electric field]. The relative concentration of donor N_D and acceptor N_A centers can be influenced by reduction treatment in oxygen octahedra ferroelectrics such as KNbO₃.

© 1988 Optical Society of America