This paper presents increase in laser damage threshold of the Nd:YAG crystal subsequent to annihilation of oxygen vacancies in the crystal structure at low dose of XeCl laser irradiation. A Nd:YAG crystal was irradiated with 500 pulses of XeCl laser (λ=308nm, τ=20 ns) at the fluence of ~100 mJ/cm 2 and 25 Hz repetition rate. The optical absorptions of the Nd:YAG crystal reduced in ultraviolet and visible regions due to elimination of some color centres indicated by UV-Vis-NIR spectra. We

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... d the laser damage threshold of the irradiated and un-irradiated crystals using 30 ns, 1064 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 mJ/cm 2 . It is nearly 5 times as high as that of un-irradiated Nd:YAG crystal, which was found to be 102±15 J/cm 2 . The present results are very important for using Nd:YAG crystals as the laser amplifier media.