Abstract

We have recently reported¹ on the formation of a large, stable second-order nonlinearity χ⁽²⁾ ~ 1 μm/V) in the near surface region (~10 μm) of commercial fused silica materials by a modest temperature and electric field poling process. This nonlinearity is approximately 10³ larger than that found in fibers and approaches the nonlinearity of LiNbO₃. We have proposed a mechanism involving mobile-ion charge transport and trapping to create a large internal field that interacts with the material χ⁽³⁾ to produce this large χ⁽²⁾ nonlinearity. In this paper, we report time-resolved measurements of the formation and decay of the nonlinearity for a sample maintained at elevated temperatures (~300°C) while the applied electric field is switched on and off. The nonlinearity is probed by monitoring the second harmonic generation with a cw mode-locked YAG laser excitation source. The observed time dependence of the nonlinearity is consistent with an ionic charge transport process.

© 1992 Optical Society of America