|
Zinc
Selenide (ZnSe)
Zinc
Selenide is used for infrared windows, lenses, and prisms where
transmission in the range 0.63µm to 18µm is desired.
Zinc Selenide has a very low absorption co-efficient and is used
extensively for high power infrared laser optics. It is non-hygroscopic.
Zinc
Selenide is a relatively soft material and scratches rather easily.
The low absorption of the material avoids the thermal runaway problems
of Germanium. Zinc Selenide requires an anti-reflection coating
due to its high refractive index if high transmission is required.
ZnSe has a fairly low dispersion across its useful transmission
range.
Zinc
Selenide, a chemically vapor deposited material, is the material
of choice for optics used in high power CO2 laser systems
due to its low absorption at 10.6µm. However it is also a
popular choice in systems operating at various bands within its
wide transmission range. ZnSe has a high resistance to thermal shock
making it the prime material for high power CO2 laser
systems. ZnSe however is only 2/3 the hardness of ZnS multi-spectral
grade but the harder anti-reflectance coatings do serve to protect
ZnSe. Zinc Selenide’s cost is about the same as ZnS multi-spectral
grade and is generally more expensive than Germanium.
| Property |
Specification |
| Transmission
Range |
0.6µm
to 16µm |
| Density |
5.27
g/cm3 |
| Thermal
Expansion |
7.1 x 10-6 /°K @ 273°K, 7.8 x 10-6 /°K @ 373°K,
8.3 x 10-6 /°K @ 473°K |
| Surface
Finish |
Typical
specifications for surface quality in the infrared are 40-20
or 60-40 scratch-dig in the 0.8 to 7µm spectral region
& 60-40, 80-50 or 120-80 scratch-dig for the 7 to 16µm
area, depending upon system performance requirements. Diamond
Turned surface finishes of 150 Å
rms or better are typical. |
| Surface
Figure |
In
the infrared, typical required surface figures range from 1/2
wave to 2 waves @ 0.6328 µm depending on the system performance
requirements. |
| AR
Coating Options |
Typical
available coatings for ZnSe include BBAR for 0.8 to 2.5µm,
3 to 5µm, 1 to 5µm, 8 to 12µm, & the 3
to 12µm spectral regions & single wavelength coating
AR at 10.6µm. Many other specialized wavelength bands
are possible within the 0.6 to 16µm range. |
| Typical
Applications |
CO2
laser systems, Thermal imaging, FLIR, Astronomical, Medical |
| Products
Manufactured |
Lenses,
Aspheric Lenses, Binary (diffractive) Lenses, Windows, Optical
Beamsplitters, Optical Filters, Prism. |
|
Wavelength
(µm)
|
Index
of Refraction (n)
|
|
1.0
|
2.4890
|
|
3.0
|
2.4380
|
|
4.0
|
2.4330
|
|
5.0
|
2.4300
|
|
7.0
|
2.4220
|
|
9.0
|
2.4120
|
|
10.6
|
2.4028
|
|
11.0
|
2.4000
|
|
13.0
|
2.3850
|
|
15.0
|
2.3670
|
|
17.0
|
2.3440
|
|
