Grating formation with very short pulses in photorefractive materials: weak excitation limit

摘要

The evolution of the space-charge field under illumination with weak very short pulses is discussed. Under a weak irradiation limit the space-charge field after recombination of the carrier becomes the same regardless of whether it is a cw, a single-pulsed, or a repetitive-pulsed excitation. On irradiation with very short pulses the space-charge field tends to increase and then decrease when the space-charge field is large owing to the nonlinear effect of the recombination term in the rate equation. With this fluctuation being neglected, the evolution of the space-charge field by mode-locked pulses becomes identical to that by cw illumination having the same averaged intensity, which was confirmed experimentally with a BaTiO3 crystal and II cw and a picosecond mode-locked Nd:YAG laser. (C) 1997 Optical Society of America.