Localized heating with a flame is shown to be a simple and effective method for substantially augmenting the photosensitivity of high-silica optical waveguides to (UV) light. The method increases the photosensitivity of standard (Ge-doped core) telecommunications fiber by a factor greater than 10 (photoinduced ΔnUV > 10−3) and renders strongly photosensitive the cores of high-quality Ge:SiO2-on-Si and Ge:SiO2-on-SiO2 planar waveguides that were negligibly photosensitive before treatment. We have written large-modulation-depth Bragg gratings, in both fiber and planar optical waveguides photosensitized by our method, using KrF (249-nm) radiation incident upon the waveguides through a zero-order-nulled phase mask. It is noteworthy that photosensitization by our method is achieved with a negligible increase in loss at the three principal optical communication windows.

Optics Letters
Department of Electronics

Albert, J, Bilodeau, F., Malo, B., Johnson, D.C., Hill, K.O., Hibino, Y., … Kawachi, M. (1993). Photosensitization of optical fiber and silica-on-silicon/silica waveguides. Optics Letters, 18(12), 953–955. doi:10.1364/OL.18.000953