Photolithography of Bragg gratings in sol-gel-derived fibers

Abstract

We report a novel photolithographic technique that facilitates the photogeneration of refractive index gratings in sol-gel derived silica fibers, based on the ability to produce changes in the index of refraction of a silica glass of the order of 0.1 to 0.001. A porous sol-gel fiber impregnated with a photosensitive organometallic compound exhibits optical changes when exposed to light. Changes in transmission and refractive index can be induced and are permanent after consolidation of the porous glass matrix. Gratings have been produced in doped sol-gel fibers by exposing the fiber to UV light through a contact mask. The photoinduced grating is permanent after heat treatment of the fiber to 1200 degree(s)C. The uncomplicated nature of this process makes this a very promising approach for the fabrication of commercial fiber optic refractive index gratings for fiber lasers, fiber optic sensors, filters, and multiplexing schemes.