Vapor transport equilibrated lithium niobate resistant to photorefractive damage

We use a combination of vapor transport equilibration and moderate MgO doping (≤1%) to explore near-stoichiometric damage resistant lithium niobate crystals with improved properties for periodic poling and annealed-proton-exchange waveguide fabrication compared to the commercially available 5-mol% MgO-doped crystals. High damage resistance, measured by the saturated space-charge field generated in the crystal by 514 nm radiation, was obtained for all MgO doping concentrations (0.3, 0.5 and 1%) with appropriate equilibration. Green-induced infrared absorption was also measured in the 0.3-% doped crystal and was below the detection limit. Dispersion in the region 460-1550 nm was measured. Periodic poling was performed using LiCl solution electrodes. Poling quality improves with lowering MgO concentration. Waveguides for frequency doubling of 1550 nm were fabricated in the 1% doped crystal with losses as low as 0.4 dB/cm and normalized efficiency of ~10%/Wcm2.