Ultraviolet-light-gating two-color photorefractive effect in Mg-doped near-stoichiometric LiNbO_3

Abstract

We investigate the ultraviolet- (UV-) light-induced two-color photorefractivity in a near-stoichiometric LiNbO3 crystal doped with Mg above the damage-resistant threshold concentration. Measurements of holographic recording and optical fixing dynamics with a 365-nm gating beam show that complementary shallow and deep gratings are formed during recording and that at least four defect centers are involved in the two-color holographic recording process. It is confirmed that UV-light-induced defect centers O− responsible for the broadband absorption changes act as shallow centers in UV-light-gating two-color holography. These findings indicate that the physical mechanism of the UV-light-gating two-color photorefractive effect in the crystal is essentially different from that of the recently reported two-color photorefractive effect in Mg-doped near-stoichiometric LiNbO3 with a 488-nm gating beam [Appl. Opt. 41, 4891 (2002)].