Two-secondary-center modeling of photorefraction and comparison with nanosecond pulse illumination experiments in barium titanate

Abstract

We report on the formation and subsequent dark evolution of induced absorption and photorefractive gratings produced by a high-intensity 15-ns pulse in an as-grown sample of BaTiO3 crystal. We show that the experimentally observed multiple time constants for decay of the induced absorption and buildup of the grating in the dark can be explained and successfully simulated by a numerical model of photorefraction incorporating two secondary (hole-trapping) centers in addition to the deep level. The model also takes into account combined electron and hole photoconductivity and high-intensity illumination. We present a full description of the method of numerical solution of the zeroth (homogeneous illumination) and the first-order parameters (inhomogeneous illumination) in this model regime for either steady-state or transient pulse trains and dark-evolution conditions.