Ge - Germanium
American Photonics optical grade germanium is used mainly in instruments and imaging systems in the wavelength range of 2 to 12µm. It can be made into windows, lenses and partial reflectors. APC germanium is non-hygroscopic, non-toxic, has good strength and thermal conductivity, and excellent surface hardness.
In CO2 laser applications, germanium is used as a 99% partial reflecting rear mirror. This allows a portion of the laser to transmit for built in power meters. Germanium has also found many applications in the military sector.