Abstract

The discovered photosensitivity of germanium-doped silica glasses, and especially the possibility of formation of refractive index gratings in the fiber core, attract much attention. The photosensitive properties of the fibers are connected with the presence of defects, namely germanium oxygen-deficient centers (GODC). The photodestruction of GODC in the fiber core by excitation of 5-eV absorption band with the following processes in the glasses is a well known way to prepare index gratings (see Fig. 1). The accepted mechanism of GODC photodestruction is photoionization with release of the electron from excited singlet state. At the same time the GODC photodestruction model, which considers triplet-state-sensitized reaction, ^vas proposed,¹ because the efficient population of triplet state by fast relaxation from excited singlet state takes place.

© 1996 Optical Society of America