The transmission range of Zinc Selenide ZnSe-CVD is 0.5 - 20 µm.

ZnSe CVD used for high power CO2 laser optics at 10.6µm, for protective optics windows or optical elements in FLIR (forward looking infrared) thermal imaging equipment, optics for medical and industrial applications (optical plane parallel windows (plates, disks, blanks), wedged windows, optical meniscus, spherical and cylindrical lenses, prisms, resonator mirrors of CO2 laser). 

The refractive index is near 2.4. Zinc Selenide has a very low absorbtion coefficient and is used extensively for high power infrared laser optic. It is non-hygroscopic.

Zinc Selenide (ZnSe) - transparent in wide spectral range from yellow (visible) to far IR. ZnSe material is a chemically inert, non-hygroscopic and highly pure product that is very effective in many optical applications due to its extremely low bulk losses, high resistance to thermal shock and stability in virtually all environments, easily machined.