Stoichiometric Mg:LiNbO_3 as an effective material for nonlinear optics

Photorefractive damage, optical absorption, photoconductivities, and photogalvanic currents of stoichiometric ${\mathrm{LiNbO}}_3$ single crystals with different Mg doping levels have been investigated. Nominally pure stoichiometric ${\mathrm{LiNbO}}_3$ shows lower photorefractive damage resistance than congruent crystal; however, stoichiometric crystals doped with MgO of more than 1.8 mol. % exhibit no measurable photorefractive damage at 532 nm to intensities of as much as $8 \mathrm{MW}/{\mathrm{cm}}^2$. This remarkable damage resistance can be attributed not only to increased photoconductivity but also to decreased photogalvanic current. Stoichiometric $\mathrm{Mg}:{\mathrm{LiNbO}}_3$ also demonstrates the shortest absorption edge, 302 nm, and a single-domain nature with low scattering losses.