Influence of XeCl laser irradiation on the laser damage threshold of the Nd:YAG crystal

A thin disc Nd:YAG crystal sample was irradiated with 500 pulses of XeCl laser ( λ = 308 nm , τ = 20 ns ) at ∼ 100 mJ / cm 2 laser fluence and 25 Hz repetition rate. The UV–Vis–NIR and additional absorption spectra of the sample showed that optical transmission of the Nd:YAG crystal increased in ultraviolet and visible regions due to elimination of some oxygen vacancies of the crystal following the irradiation. Increase in laser damage threshold of the Nd:YAG crystal sample subsequent to annihilation of oxygen vacancies was obtained by the laser damage threshold experiment. The laser damage thresholds of the irradiated and un-irradiated crystals were measured using 30 ns, 1,064 nm single longitudinal mode, TEM 00 pulses of a passively Q-switched Nd:YAG laser. The laser damage threshold of the irradiated crystal (after dividing by √ 3 to scale for pulse duration of 10 ns) was obtained to be 501 ± 50 J / cm 2 . It is nearly five times as high as that of un-irradiated Nd:YAG crystal, which was found to be 102 ± 15 J / cm 2 .