Changes in the refractive index of amorphous chalcogenide ${\mathrm{A}}_2{\mathrm{S}}_8$ films upon ultraviolet (UV) exposure and annealing at different temperatures are investigated in detail, indicating an index contrast of the order of ${10}^{-2}$ in the ${\mathrm{A}}_2{\mathrm{S}}_8$ channel waveguide. An ${\mathrm{As}}_2{\mathrm{S}}_8$ channel waveguide is fabricated using UV well irradiation and then annealing near the glass transition temperature and shows a low propagation loss of $0.76\mathrm{dB}/\mathrm{cm}$ and good propagation characterization at the $1310\mathrm{nm}$ guided mode.