Thermal Poling of Silica

Glass, an amorphous centrosymmetric material, naturally exhibits no second-order optical susceptibility (chi2). Therefore typical second-order effects such as electrooptic effect or second harmonic generation do not exist. During thermal poling we applied a high voltage (kV-range) on a silica sample, which was heated up before to 270-330°C. After cooling and switching off the voltage, a frozen-in electric field exists in the material (EDC~107 V/m). This electric field breaks the inversion symmetry, and in combination with the intrinsic third-order nonlinearity an effective susceptibility chi2eff ~ chi3*EDC arises. This poled samples were characterised by second harmonic measurements. We will report on the influence of different poling-parameters (voltage, length of time, temperature) on second harmonic generation, as well as on the stability of the generated second-order nonlinearity concerning UV-radiation, temperature and aging.