Abstract

Optical fiber photosensitivity can be triggered by photochemical processes associated with a large variety of dopants. Thus, photosensitivity in germanosilicate fibers has been related to absorption of light at a germanium defect absorption band located near 5 eV [1] [2]. Photosensitivity in rare-earth doped glasses or optical fibers has been demonstrated by pumping of ion transitions. For example, we have recently reported permanent index changes in Ce³⁺ doped ZBLAN, HBLAN and ZBLALi fluorozirconate glasses or fibers through the pumping of 4f → 5d Ce³⁺ transitions using a pulsed laser [3] [4]. In most of the experiments dealing with rare-earth or germanium doped glasses or fibers, it was reported that grating inscriptions led to broad absorption changes which were attributed to photoinduced charge transfer from donors to trap sites. This suggests that charge transfer is a common effect involved in grating photoinscription within all the up to now studied insulating glass fibers. Experiments have been carried out with a view to finding other analogies or differences between photosensitive behaviors of gratings written in various glasses. The aim of the talk is to report results of these experiments with a specific emphasis on the dynamics of grating formation.

© 1995 Optical Society of America