Time-dependent decay of quadratic non-linearity in corona-poled silicate glass films

Quadratic optical effects in corona-poled silicate glass films on glass substrates were investigated using second harmonic generation. A time-dependent decay of the quadratic non-linear coefficients observed at room temperature was found to be composed of two components which have different relaxation times. The slow decay component increased with an increase of BaO-B2O3 or BaO-Al2O3 in the glass composition and with a decrease in the film thickness. The quadratic non-linearity showing the slow decay is assumed to be ascribed to a microscopic change in a local structure of I:he glass films. On the other hand, the fast decay component is suggested to be caused by a static-electric field in the entire film which formed by the induced surface charge and the space charge at the interface between the film and the substrate.