The highly optical damage resistance of lithium niobate crystals doping with Mg near its second threshold

In the last meeting (TOPS 62, 166 (2001)), we deduced that there should exit a second threshold of Mg in lithium niobate (LiNbO3) and when the doping concentrations of Mg reach this threshold LiNbO3 crystals will have excellent ability to resist optical damage. In this study, we obtained several nearly stoichiometric LiNbO3 Crystals with the doping concentration of Mg near the second threshold with the help of vapor transport equilibrium (VTE) technique. These crystals show, up to now, the best resistant ability against laser induced optical damage: no laser beam distortion was observed under a light intensity of 26 MW/cm(2), and only a Delta n of 4.6x10(-7) was measured by two-beam holographic recording.