The transmission wavelength for Monocrystal Germanium is 2-12um, it is a common infrared crystal which is widely used for infrared image system and infrared spectrograph systems. Ge has a small absorbency at 10.6um. It is a good material for CO2 lens and windows
Manufacture Specifications

Diameter:3mm to 280mm

Diameter Tol.+/-0.1

Surface Quality:40-20 standard

Surface Quality:40/20

Flatness :1/4 lambda

Chamfer:0.25mmx45degree

Focal Length Tol.+/-1%

Coating:Customer design