Depth profiling of the <i>d</i>33 nonlinear coefficient in annealed proton exchanged LiNbO3 waveguides

Abstract

We report depth profiling of the d33 nonlinear coefficient in annealed proton exchanged LiNbO3 waveguides using reflected second-harmonic generation from angle-lapped samples. At depths greater than the initial proton exchange depth the d33 coefficient retains nearly its bulk LiNbO3 value, but within the initial proton exchange region the value of d33 varies with annealing time. These results reconcile previous conflicting measurements of the d33 coefficient and explain the variation in the efficiency of guided wave frequency conversion devices with annealing.