Time-Dependent Nonlinear Photorefractive Response to Sinusoidal Intensity Gratings
The time-dependent, nonlinear Kukhtarev equations are numerically solved to determine the temporal and spatial dependence of the space-charge field for a sinusoidal intensity profile with an arbitrary modulation depth m. The intensity profile is spatially bounded simulating two interfering laser beams of finite spot size. The numerical solution allows us to critically examine the validity of analytical theories for linear and nonlinear photorefractive effects. The parametric dependence of the characteristic time constant τ for writing a grating is studied including the effects of quiescent intensity I0, modulation index m and the thermal ionization rate β. We find that the Kukhtarev equations inherently yield a sublinear dependence of the characteristic time constant τ on I0 even for a single trap (acceptor) species when I0 is above a critical value Ic. Expression for Ic is given in terms of material properties, and the sublinearity index is determined for BSO. The exact dependence of τ on the modulation index (0 < m ≤ 1) is determined for BSO, and the nonsinusoidal waveform of the space-charge field for large m is fully characterized both analytically and numerically.
Copyright © 1997, Elsevier
Singh, Nagendra; Nadar, S. P.; and Banerjee, Partha P., "Time-Dependent Nonlinear Photorefractive Response to Sinusoidal Intensity Gratings" (1997). Electrical and Computer Engineering Faculty Publications. 173.