Thermal poling and space charge dynamics including surface impurity injection in fused silica

The space charge region associated with the second-order nonlinearity in thermally poled fused silica was examined using secondary ion mass spectrometry (SIMS). Results for four samples are presented here: two flame-fused quartz samples (type-II fused silica), a higher purity flame-fused synthetic (type-III) fused silica, and a type-II fused silica treated with deuterated water. SIMS results show: 1) ionic depletion regions formed by migration of alkali ion impurities with different mobilities, 2) injection of surface alkali contaminants arising from the high surface fields, and 3) evidence of field injection as well as thermal diffusion of adsorbed surface water.