VISUALIZATION OF THE NONLINEAR-OPTICAL SPACE-CHARGE REGION OF BULK THERMALLY PALED FUSED-SILICA GLASS

We etched thermally poled fused-silica coverslips in 49% HF for 30 s t ransverse to the poling direction to reveal structural details of the nonlinear region. A peaked ridge below the anode surface, correspondin g to a slower etch rate than that of the bulk SiO2, was located simila r to 5 mu m below the anode surface for a poling time of 30 s. The rid ge moved deeper into the glass logarithmically with poling time. This trend is qualitatively consistent with a recent model for the formatio n of the space-charge region that includes injection of hydrogen ions at the anode surface. (C) 1998 Optical Society of America.