Strong Bragg gratings photoinduced by 633-nm illumination in evaporated As_2Se_3 thin films

Bragg gratings are used in several photonic devices to reflect, and thus to isolate, specific wavelengths of light. Gratings can be photoinduced in chalcogenide glasses by illumination of bandgap light in an interference pattern. We used holographic interferometry to create Bragg gratings in amorphous ${\mathrm{As}}_2{\mathrm{Se}}_3$ thin films with a period of $0.56 \mathit{\mu }\mathrm{m}$ by illumination with 633-nm light. The quality of the gratings was tested in real time, and refractive-index modulations as high as 0.037 were measured. These gratings were found to be stable over a period of several months if they were kept in the dark.