Theoretical study on grating formation in photovoltaic photorefractive LiNbO3 crystal with short light pulses

Based on Valley's quasi-cw approximation, the grating formation in materials exhibiting bulk photovoltaic effect on illumination with short light pulses (such as ns pulses) is investigated. We give the expression of the space-charge field, and find that it has two time constants. When considering and not considering the photovoltaic effect, the diagrams of two time constants as a function of irradiance in units of 1/(s tau(R)) are the same. The energy required to erase a grating to 1/e of its initial value is also studied in the two cases. The two results are also the same.