Optical Damage Resistance and Refractive Indices in Near-Stoichiometric MgO-Doped LiNbO3

Abstract

The optical damage resistances of near-stoichiometric LiNbO3 (LN) crystals doped with MgO were investigated at λ=532 nm. Their refractive indices were also measured in the wavelength range from 440 to 1050 nm, from which Sellmeier's equations were derived. While the congruent LN (CLN) crystal required 5 mol% MgO to suppress the optical damage, the near-stoichiometric LN (SLN) crystal doped with 1 mol% MgO showed no optical damage up to the input intensity of 2 MW/cm2. The ordinary refractive indices (no) of MgO-doped SLN crystals decreased with MgO doping concentration up to 4.6 mol%. In contrast, the extraordinary refractive indices (ne) of MgO-doped SLN crystals were found to be almost independent of MgO doping concentration up to 4.6 mol%. With respect to optical device design, it is advantageous that ne of MgO-doped SLN crystal is almost independent of MgO doping concentration up to 4.6 mol% and that the SLN crystal needs only 1 mol% MgO to suppress optical damage.