Near-stoichiometric and Mg-doped LiTaO3 for fast interband photorefraction

In this paper, interband photorefraction was demonstrated in near-stoichiometric LiTaO₃ at the deep ultraviolet wavelength λ_UV= 257 nm. The photoconductivity of near-stoichiometric LiTaO₃ at this wavelength was determined, and Bragg diffraction was investigated. The formation of two distinct grating components, which are most likely associated with free carriers on the one hand and deep traps on the other hand, was observed in depth-resolved measurements. We demonstrate that by controlling the stoichiometry the response time and dynamic range of the interband photorefractive effect can be very much improved. Measured time constants were in the order of a few tens of milliseconds for UV light intensities of about 100 mW/cm², three orders of magnitude faster than time constants reported previously for conventional photorefraction in near-stoichiometric LiTaO₃ at 364 nm.