(Ge) is most widely used for lenses and windows in IR systems
operating in the 2 - 12 µm range. The enviroment does not make any
problems because Germanium is inert, mechanically rugged, and fairly
hard. It is an excellent choice for multi-spectral systems and for applications
where EMI shielding is necessary. Germanium can be electrically heated
for anti-fogging or anti-icing applications. We
do not manufacture Germanium, but hold stock of Czochralsky grown material
of various diameters. It can be used as a polycrystalline or as a single
crystal. The purity should correspond to an electrical resistivity of
at least 20 to 30 Ohm/cm, either p- or n-type to avoid absorption bands.
The high retractive index makes AR-coating essential.
(Si) is commonly used as a substrate material for infrared reflectors
and windows in the 1.5 - 8 µm region. The strong absorption band
at 9 µm makes it unsuitable for CO2-laser transmission
applications, but it is frequently used for laser mirrors because of
its high thermal conductivity and low density. Silicon is also a usefull
transmitter in the 20 µm range.