Cadmium Telluride (CdTe)

Cadmium Telluride is the most dense of the common infrared transmitting materials and has one of the widest transmission ranges of any infrared material. Cadmium Telluride is chiefly used as a filter substrate in the 12 – 25µm region where many other IR materials have absorption bands, It is also used in CO2 laser systems, particularly as output couplers, but only when the power level is low (time-averaged power below several hundred Watts) since its absorption is as low as that of ZnSe but its thermal conductivity is one third that of ZnSe. Cadmium Telluride is more expensive than Germanium or Zinc Selenide. It has less than half the hardness of ZnSe.

The current available size limitation for Cadmium Telluride is about 72mm diameter. The useful transmission of CdTe extends from about 1µm to 25µm. Its index varies from about 2.7 to 2.4 in range (n=2.67 @ 10.6µm).

 

Property Specification
Transmission Range 1µm to 25µm
Density 5-85
g/cm3
Thermal Expansion 5.9 x 10-6 /°C @ 20°C
Co-Efficient
Surface Finish Typical specifications for surface quality in the infrared are a 40-20 scratch-dig in the 1 to 3µm spectral region & 60-40 scratch-dig for the 3-7µm area, & 60-40, 80-50 or 120-80 scratch-dig above 7µm depending on system performance requirements. CdTe is Diamond Turnable.
Surface Figure In the infrared, typical required surface figure ranges from 1/2 wave to 2 waves @ 0.6328µm & is specified depending on the system performance requirements.
AR Coating Options CdTe can be anti-reflectance coated for various wavelengths or wavelength ranges between 1 & 25µm.
Typical Applications Thermal Imaging, Low power CO2 laser systems.
Products Manufactured Lenses, Aspheric lenses, Windows, Wedges, Prisms.

 

Wavelength (µm)
Index of Refraction (n)
4.0
2.70
10.0
2.68
18.0
2.64