Strong fibre Bragg-gratings written in highly photosensitive Sn-doped fibres without H₂-loading using KrF excimer and UV copper vapour lasers

Sn-doped silica optical fibres are temperature resistant, have high photosensitivity and low loss at 1.55 µm, properties which make them desirable for use in telecom components and sensors. Results of the fabrication of Bragg gratings in Sn-doped fibres using KrF excimer and UV copper vapour lasers will be presented. 1. Introduction Since the first observation in 1978 by Hill and co-workers [l], photosensitivity has launched many new fields in telecom and fibre optic based devices. In the last decade many papers have been published showing enormous progress both in grating writing techniques and fibre fabrication. New materials have been studied to increase the photosensitivity of telecom optical fibres that would otherwise be insufficient for many applications. SnO2-doping was proposed as a convenient co-dopant [2,3,4,5] because of its low-absorption in the third telecom window at 1.55 µm and high photosensitivity when exposed to 248 KrF excimer laser (KEL) radiation. Recently it was demonstrated that the reflectivity of gratings written with frequency-doubled copper vapour laser (CVL) is similar to the reflectivity of the gratings written with the frequency-doubled argon ion laser [6] . Moreover, the CVL can be used to write simultaneous multiple gratings with identical reflectivity [6,7]. In this work we study the photosensitivity of tin-doped fibres with the CVL and compare it to the photosensitivity achieved with the KEL