We report a novel method to increase the UV photosensitivity of GeO<sub>2</sub>: SiO<sub>2</sub> optical fibers based on exposure to CO<sub>2</sub> laser irradiation before grating writing. Fibers treated with a CO<sub>2</sub> laser can produce gratings with refractive-index modulation two times greater and a Bragg wavelength that can be 2 nm longer than those of untreated fibers. Experiments on GeO<sub>2</sub>: SiO<sub>2</sub> preform samples treated with a CO<sub>2</sub> laser in a way similar to the fibers showed a marked increase of the 242-nm absorption band, which is associated with an increase of germanium oxygen-deficient centers and is believed to be responsible for the higher photorefractive response.
© 1999 Optical Society of America
(050.1950) Diffraction and gratings : Diffraction gratings
(060.2310) Fiber optics and optical communications : Fiber optics
(160.5320) Materials : Photorefractive materials
(260.7190) Physical optics : Ultraviolet
G. Brambilla, V. Pruneri, L. Reekie, and D. N. Payne, "Enhanced photosensitivity in germanosilicate fibers exposed to CO2 laser radiation," Opt. Lett. 24, 1023-1025 (1999)