Large second-order optical nonlinearity in thermally poled high-purity silica glass

Summary form only given. Since Myers et al. have observed a permanent large second-order optical nonlinearity in silica glass poled by applying 5 kV/mm at 260/spl deg/C, silica glass has become much more attractive material for photonic devices. They obtained /spl chi//sub 33/ of 1 pm/V in fused silica glass made from natural quartz, and considered the metallic ions included in the glass have largely relevant to the nonlinearity. Very high-purity silica glass is much desirable for optical devices, which is synthesized artificially from silane or other salts. On the contrary, such high-purity glass did not show second-order optical nonlinearity even in the samples poled under the same conditions as for the fused silica glass mentioned above. In our previous paper, we have found that second-order optical nonlinearity has been induced in high-purity silica glass exposed to X-ray radiation before poling, at though the /spl chi//sub 33/ value is as small as 0.24 pm/V. In this paper, we show that much larger second-order optical nonlinearity of 0.8 pm/V is induced in high-purity silica glass treated at 700/spl deg/C and exposed to KrF excimer laser pulses before poling and then discuss about the formation mechanism.