Abstract: An optical window is provided, particularly for multispectral or broadband wavelength (visible and infrared) transmission, which is resistant to damage or erosion by high velocity raindrops or other adverse environmental conditions. The window consists of a substrate of material having the necessary optical properties for the desired spectral range, with a cladding or protective layer of material of high resistance to erosion or other damage bonded to the substrate by a glass bonding material. While any suitable materials meeting the optical and physical requirements may be used, the substrate may be a material such as zinc selenide with a protective layer of zinc sulfide bonded to the substrate by a thin layer of a chalcogenide glass.