Large Second-Order Nonlinearity in Bulk and Thin-Film SiO2

Abstract

We have previously reported1 the observation of a large second-order nonlinearity in the near surface region of commercially available fused SiO2 windows induced by a combined temperature (200-325°C) and electric field (~ 30 kV/cm) preparation process. This preparation process includes heating the sample, in laboratory atmosphere, while applying a DC bias of 3-5 kV across the ~1.6 mm-thick samples with electrodes that are simply physically contacted to the sample. After several minutes at temperature, the sample is allowed to cool to room temperature with the bias field maintained. Following cooling, the bias field and the electrodes are removed and a permanent second-order nonlinearity is observed. This nonlinearity is monitored by second-harmonic generation, in transmission, using a Q-switched YAG laser source at 1.06 pm focused to an intensity of ~ 10MW/cm2.