Oxygen-deficiency effect on thermal poling of silica-based glasses

Thermal poling has been investigated in silica-based glasses prepared by the sol-gel method. Samples with different OH-content (from 40 ppm to few 103 ppm), doping (oxygen-vacancies, substitutional Sn, SnO2 clusters) and post-synthesis treatment (X-ray irradiation) have been heated in vacuum at 280 °C with an applied voltage of 4 kV. Second-order non-linearity has been observed after poling, with χ(2) of the order of 0.1 pm/V. The comparison among samples suggests that OH-content is not the only factor responsible for the observed non-linearity.