Photosensitive index changes in germania-doped silica glass fibers and waveguides

Recent developments in the photosensitivity of germania doped silica glass are reviewed. The cause and nature of the absorption band centered near 240 nm are discussed and possible structures for this defect are reported together with a summary of the proposed mechanisms for the UV index change. Experimental techniques for assessing the refractive index change are listed and this leads to a consideration of the effects of non-ideal grating formation. Mechanisms for enhancing the photosensitivity of fibers and germania doped silica films are assessed using a systematic study of the photosensitivity of fibers fabricated under the different techniques. Finally some of the possible applications for photosensitivity are briefly discussed.