An Ion Exchange Model for Extended-Duration Thermal Poling of Bulk Fused Silica

Thermal poling induces a strong second-order nonlinearity in bulk fused silica.1 The non-linearity occurs on the anode side of the poled glass; various measurements have shown that the nonlinear region is ~ 5 to 15 μm thick; and that the nonlinearity scales linearly with the applied poling voltage. The formation of the nonlinearity is a dynamic process involving mobile ionic charge carriers.2 We present experimental observations of additional aspects of this dynamic process along with a model that demonstrates that ion exchange can play a role in the formation of the nonlinearity.