Zinc Selenide, produced by the method of chemical vapour deposition, is the preferred material for optics used in high power CO2 laser systems due to its low absorption at 10.6um. However it is also a popular choice in systems operating at various bands within its wide transmission range. ZnSe has a high resistance to thermal shock making it the best material for high power CO2 laser systems. ZnSe however is only 2/3 the hardness of ZnS multi-specral grade but the harder anti-reflectance coatings do serve to protect ZnSe. Zinc Selenide is a relatively soft material and scratches rather easily. It requires an anti- reflection coating due to its high refractive index if high transmission is required. ZnSe has a rather low dispersion across its useful transmission range. For high power applications, it is critical that the material bulk absorption and internal defect structure be carefully controlled, that minimum-damage polishing technology be employed, and the highest quality optical thin film coatings are used.