Bulk photovoltaic effect and photorefractive grating formation in lithium niobate with picosecond light pulses

摘要

I investigated photorefractive grating formation in materials exhibiting the bulk photovoltaic effect on illumination with weak, very short light pulses. For a light pulse shorter than the time constants of the carrier, the existing theory of grating formation, as well as the expression for the photovoltaic current, breaks down. Nevertheless, my experiment, which is the first quantitative comparison of this kind to my knowledge, showed no meaningful difference between the pulsed and ew excitations of Fe:LiNbO3 for the same average intensity. I developed a simple model in which the bulk photovoltaic effect was implemented as a spatial shift in the initial carrier distribution, and I derived an analytical expression for the space-charge field. The resulting expression agreed with that of the quasi-cw approximation in the limit of a small spatial shift, thus supporting my experimental results. (C) 2001 Optical Society of America. [References: 20]