First- and second-order Bragg reflectors at telecommunication wavelength (1.5 m) were fabricated in single-mode monolayer (As2S3) and multilayer (As-S-Se/As-S) chalcogenide glass (ChG) planar waveguides with near bandgap illumination using an interferometric technique. Reflectivities as high as 90% near 1555 nm, and index modulations up to 3 10 - 4 were achieved. The volume photodarkening effect is the principal mechanism involved in the formation of the Bragg gratings.
Ali Saliminia, Alain Villeneuve, Tigran V. Galstyan, Sophie LaRochelle, and Kathleen Richardson, "First- and Second-Order Bragg Gratings in Single-Mode Planar Waveguides of Chalcogenide Glasses," J. Lightwave Technol. 17, 837- (1999)