As2S8 planar waveguide: refractive index changes following an annealing and irradiation and annealing cycle, and light propagation features

The refractive index of as-evaporated amorphous semiconductor As2S8 film upon an annealing and saturation irradiation and annealing cycle is reversible. Upon successive treatment with annealing and non-saturation irradiation and further annealing, the refractive index of the as-evaporated amorphous semiconductor As2S8 film reaches a maximum value and then its reversibility occurs upon annealing. The annealing of the amorphous semiconductor As2S8 films results in the stabilization of the structure through changes of the S-S bonds in the nearest environment, accompanied by a decrease of film thickness. The As2S8 planar waveguide after annealing (130 °C) and saturation irradiation and annealing (130 °C) shows a good propagation characteristic with ca. 0.27 dB/cm low propagation loss of the 632.8 nm guided mode.