Rapid Thermal Annealing of Chalcogenide glasses for Photodarkened Waveguide and Grating Applications

Optical elements for applications in communications and interconnections such as waveguides and grating devices can be patterned in chalcogenide glasses by illumination with above band gap light, which causes photodarkening1. Photodarkening is a photo-induced red shift of the optical absorption edge and is accompanied by an increase in the index of refraction in the transparent spectral range below the absorption edge. A configurational model2 describes photodarkening as an illumination induced transformation from a stable configuration to a quasi-stable configuration via an electronically excited state. Annealing close to the glass transition temperature (Tg) causes a direct structural relaxation from the quasi-stable to stable state.