Mx. Qiu et al., Threshold conditions for bulk second-order nonlinearity and near-surface second-order nonlinearity in thermally poled Infrasil silica, OPT REV, 8(3), 2001, pp. 159-162
Generation of bulk second-order nonlinearity in silica glass requires highe
r poling temperature or longer poling time than that of near-surface second
-order nonlinearity. The threshold conditions for initiating the bulk secon
d-order nonlinearity are studied on Infrasil fused silica glass. The thresh
old poling time is strongly dependent on the poling temperature. The near-s
urface second-order nonlinearity is also studied, especially the dependence
of thickness of the nonlinear layer on the poling temperature, poling volt
age and poling time. Secondary-ion mass-spectroscopy measurement showed dep
letion of Na+ ions at the anodic surface. We assume there is an ionic wave
during poling traveling from the anodic surface to generate the dipolar ele
ctric field that induces the near-surface second-order nonlinearity.