Numerical simulation of the propagation of a single laser pulse in a photorefractive medium

The paper presents a numerical study of the self-focusing time behaviour of a ns single laser pulse propagating in a biased photorefractive sillenite crystal. Assuming particular hypotheses in the case of short pulse illumination, a nonlinear partial differential equation linking the refraction index and the beam intensity has been derived from a mono-dimensional Kukhtarev band transport model. The numerical resolution of this equation has been coupled to the simulation of the propagation of a beam in a nonlinear medium using a Beam Propagation Method. We thus simulate the self-focusing phenomena of a single laser pulse on the nanosecond time-scale. These calculations let us describe the output beam profile evolution during the laser pulse and study theoretically the influence of different parameters on self-focusing such as the applied electric field, the beam intensity and waist. A successful comparison to previous experimental measurements is reported.