Influence of wave-mixing on the optical damage-threshold of LiB 3 O 5 crystals during generation of ultraviolet laser light

Laser-induced optical damage upon wave-mixing is investigated in single crystals of lithium triborate. Surface and bulk damages appear after simultaneous exposure to intense infrared, green and ultraviolet pulsed laser light. The build-up of a light-induced refractive index lense during the process of sum-frequency generation ( = 1064 nm+ = 532 nm ? = 355 nm) is suggested and we discuss the role of multi-photon absorption processes for the appearance of the damage.