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 there combination 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 BaTiO<sub>3</sub>crystal and a cw and a picosecond mode-locked Nd:YAG laser.
© 1997 Optical Society of America
Hideki Okamura, Kazuo Takeuchi, Takuya Tanaka, and Kazuo Kuroda, "Grating formation with very short pulses in photorefractive materials: weak excitation limit," J. Opt. Soc. Am. B 14, 2650-2656 (1997)