Infra-red Windows
Many
different types of material will transmit the infra-red.
Selection of the most appropriate material is usually made with reference
to the extent of the required transmittance and the nature of the environments
being isolated by the window.
Zinc
Selenide , Zinc Sulphide , Germanium or
Gallium Arsenide are commonly used for the broad IR spectrum including both 3-5
μm and 8-14 μm bands. Cleartran
is a form of Zinc Sulphide with improved visible transmittance.
Calcium
Fluoride and Magnesium Fluoride are used in the 3-5 μm band while
maintaining high transmittance in the visible.
Potassium Bromide has the widest transmission spectrum but is extremely
soft and also hygroscopic. Here are
some of the commonly available materials (see datasheet for more information):
ZnSe, ZnS, Cleartran, Ge, Si, GaAs, CaF2
Typical
diameters offered are: 6.35, 9.53, 12.7, 19.1, 25.4, 27.9, 38.1, 50.8, 63.5 and
76.3 mm.
Thickness
varies from 2.0 to 7.0 mm as appropriate to maintain the flatness specification.
These
windows are normally supplied uncoated but we can offer a range of
anti-reflection coatings for broadband, narrow-band or dual wavelength
applications. Please ask about
coatings.