ZnS Multispectral (water-clear) is used for IR windows and lenses in the thermal band (8 to 14 μm) where maximum transmission and lowest absorption is required. Also selected for use where visible alignment is an advantage.
ZnSe is used widely for IR components, windows and lenses, and for spectroscopic ATR prisms. Zinc Selenide is one of the materials of choice for CO2 laser optics operating at 10.6 microns.
N-BK7 is a Schott designation for the most common Borosilicate Crown glass used for a wide variety of visible applications. The basic data here is given for N-BK7. Full optical design data on N-BK7 and other glasses can be found by following the web links at the bottom of this page.