Germanium (Ge) windows are transparent in the infrared wavelengths from 1.8um to 23um, It is especially used as the front optic in thermal imaging cameras working in the 8 to 14 micron range for passive thermal imaging and for hot-spot detection in military, mobile night vision, and fire fighting applications. It is used in infrared spectroscopes and other optical equipment that require extremely sensitive infrared detectors.
ZnSe is used widely for IR components, is transparent over an extremely wide range of wavelength 0.6um-21. When free of absorption and inclusions it is ideally suited for CO2 laser optics at 10.6 µm wavelength.
