A novel technique to determine second-order optical nonlinearity profiles

We report a novel technique to determine uniquely the second-order nonlinearity profile of nonlinear films. Applied to a thermally poled silica sample, it reveals a stronger coefficient d₃₃ (0.8 pm/V) than previously reported and important new profile features. Thermal poling is an interesting and potentially important technique used to induce a second-order optical nonlinearity in silica. This new and powerful technique is predicted to measure the nonlinearity and the nonlinearity profile of poled glasses and other nonlinear films.