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Lithium Fluoride (LiF)
Lithium Fluoride has the lowest index of refraction of all the common infrared materials. LiF is slightly plastic, and has a relatively high thermal expansion coefficient. It is also the most expensive of the Fluoride series of crystals.
| Property |
Specification |
| Transmission Range |
0.121µm to 5.0µm |
| Density |
2.639 g/cm3 |
| Thermal Expansion |
37 x 10-6 /°C |
| Surface Finish |
Typical specifications for surface quality in the infrared are a 40-20 scratch dig in the 0.75 to µm spectral region and 60-40 or 80-50 scratch-dig for the 3-7µm area depending upon system performance requirements. LiF is diamond turnable. |
| Surface Figure |
In the infrared, typical surface figure ranges from 1/2 wave to 4 waves @ 0.6328µm depending upon system performance requirements. |
| AR Coating Options |
LiF can be AR coated for use in the infrared, but generally without much improvement in transmission due to its low index of refraction and already high transmission |
| Typical Applications |
Thermal imaging, Astronomical, Excimer laser applications. |
| Products Manufactured |
Lenses, Aspheric lenses, Windows, Wedges, Prisms. |
|
Wavelength (µm)
|
Index of Refraction (n)
|
|
1.0
|
1.387
|
|
2.0
|
1.379
|
|
3.0
|
1.367
|
|
4.0
|
1.349
|
|
5.0
|
1.327
|
|
5.8
|
1.304
|
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