Investigation of nonlinear absorption and laser damage on lithium niobate single crystals

The thresholds of surface and bulk damage by 10 ns Nd:YAG laser in LN single crystals are measured. The accumulation effect produced by multipulse laser irradiation is also investigated. Temporal transmission measurement is employed to monitor the nonlinear absorption in the crystals during YAG laser irradiation. It turns out that the multiphoton absorption is the main damage mechanism in both surface and bulk damage processes. The direct reasons leading to visible damage are the accompanied stress explosion in the bulk and the thermal melting and etching on the surface. The multipulse damage is mainly the effect of the accumulation of micro-damages.