Protective coatings of CVD diamond have been bonded to infrared-transmitting optical windows of ZnSe with As-Se-S system chalcogenide glasses of which the refractive index is made to closely match that of diamond by the "optical brazing" process. To select optimal composition in the As-Se-S system, the T-g, T-s, reflective index and infrared-transmittance of the glass samples were measured. Measurement of transmittance with a Fourier transform infrared spectrometer after the brazing process confirmed that scattering losses were greatly reduced. Infrared transmittance of ZnSe windows with a thin film diamond coating bonded to chalcogenide glass was about 63%.