Mechanisms of Bragg grating formation in UV hypersensitized standard germanosilicate fibers with KrF laser light

摘要

Bragg gratings have been UV written in UV hypersensitized standard fibers through exposure of a phase mask to KrF laser light. On the other hand, LTV hypersensitized preform plates and fibers have been postexposed in conditions similar to those used to write the gratings. Vacuum-UV and IR absorption spectroscopy has been carried out with a view of monitoring the kinetics of formation (or bleaching) of defect-associated bands. The fluence per pulse F-i was the parameter of the exposures. The dependence of the refractive index changes on fluence per pulse points to a two-photon absorption mechanism for Bragg grating inscription. This dependence is correlated to the one for the GeE' defect and OH species-related absorption bands and discussed within the framework of a two-step model. (c) 2006 Optical Society of America.