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

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, O-2, and H-2 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. (C) 2002 Optical Society of America.