Limitation of optical poling in germanium-silicate glasses

The giant increase of the absorption of the radiation with the doubled frequency in a region of high values of the optically-induced electric fields (about 10(5)-10(6) V/cm) has been observed during the investigation of the optical poling process in germanium-silicate glass. The absorption suppresses the writing of the second-order susceptibility grating and leads to the restriction of the maximum efficiency of the photoinduced second harmonic generation in glass. We demonstrate that the observed effect is not anisotropic and may be considered as a consequence of a competition between the charge separation by the local trapping levels due to electrostricted photoinduced phonons and recombination diffusion of carriers. (C) 2003 Elsevier B.V. All rights reserved.