Two photon absorption and photoconductivity in photosensitive glasses

In this paper we present experimental evidence for the creation of defects in Ge doped silica by exposure to intense visible or UV light. The presence of the defects is detected by an increase in two photon absorption at 1053 nm and an increase in photoconductivity at 488 nm. This provides evidence to support models for photoinduced second harmonic generation based on interference between single photon absorption of visible light and two photon absorption of IR light. In as much as photoinduced SHG has been observed in many other glass systems, results from this paper can be generalized to provide a picture of photoinduced SHG in solid, centrosymmetric systems.