Temperature distribution and thermal-induced defects in photorefractive barium titanate crystals illuminated with intense cw or pulsed laser irradiations

The temperature distribution in a parallelepipedic crystal irradiated with a Gaussian repartition of light is calculated by solving the three-dimensio nal heat equation and taking into account the losses through the sides of t he samples. The theoretical and experimental maps of temperature are satisf actorily compared. For barium titanate crystals, the resistance to intense cw laser (25.7 kW/mm(2) at 514.5 nm) and to Nd:YAG pulsed laser (peak power of 9.2 MW at 532 nm) is investigated. The defects induced by the irradiati on are analysed. Under pulsed illumination, the damage threshold is found t o be 0.54 GW/cm(2) in a nominally undoped BaTiO3 and 0.44 GW/cm(2) in a rho dium-cobalt doped BaTiO3 crystal.