Generation and erasure of second-order optical nonlinearities in thermally poled silica glasses by control of point defects

Abstract

Ultraviolet laser pulses were found to introduce and destroy point defects that play a key role in the generation of second-order optical nonlinearities by thermal poling in high-purity silica glasses. The characteristics of the generation process depended largely on not only ≡Si—OH,O2, and H2 content of the glasses but also the sequence of thermal poling and the pulse irradiation. There were two different kinds of nonlinearity: one localized in a thin layer near the sample surface (near-surface) and a bulk one spreading throughout the sample. The near-surface and bulk nonlinearities are associated with ≡Si—O- and ≡Si⋯Si≡, respectively.