BRAGG GRATING FABRICATION IN GERMANOSILICATE FIBERS BY USE OF NEAR-UVLIGHT - A NEW PATHWAY FOR REFRACTIVE-INDEX CHANGES

Using 334-nm light, we demonstrate side writing of Bragg gratings with an index change of similar to 10(-4) in germanium-doped fibers. No hy drogen loading of the fibers was required. These gratings have the sam e temperature stability as gratings fabricated with 240-nm light. Our results suggest that photoionization is not needed for formation of gr atings in Ge-doped glass. me observe an enhancement of the 334-nm phot osensitivity in boron-codoped fibers and suggest that B facilitates a structural transformation of the glass. (C) 1997 Optical Society of Am erica.