Holographic gratings in pure and Mg-doped near-stoichiometric LiTaO3 induced by deep-ultraviolet light

Interband photorefractive gratings induced by deep ultraviolet light at λUV = 257 nm are investigated in pure and Mg-doped near-stoichiometric LiTaO3. By controlling the stoichiometry, the response time and dynamic range of the interband photorefractive effect can be very much improved. Measured time constants are in the order of a few tens of milliseconds for UV light intensities of about 100 mW/cm2. Further, we report that Mg doping of near-stoichiometric LiTaO3 increases the grating response rate by a factor of 50 compared with the one in undoped crystals. In Mg-doped near-stoichiometric LiTaO3, quasi-fixing of holographic gratings with UV light and nondestructive readout in the visible has been observed. These quasi-fixed gratings are written in the deep traps of the crystal.