CaF2 (Calcium Fluoride)

Download CaF2 (Calcium Fluoride) Datasheet (PDF, 158 KB)


CaF2 (Calcium Fluoride) is widespread material for UV and IR spectroscopy from 0.15 to 9 transmission range as well as for laser applications. The crystal is optically isotropic, non-hygrоscopic and insoluble in most acids and alkali therefore the polished surfaces are practically not degraded in normal atmospheric conditions. A high mechanical strength makes it useful for high pressure applications. At the same time it is very sensitive to thermal shock. Low refraction index of CaF2 makes it possible to be used without anti-reflection coating for non-laser applications.


  • UV, IR, FTIR spectroscopy
  • Laser spectroscopy

Product types:

  • Plane-parallel windows and wedges
  • Beamsplitter substrates for FTIR spectroscopy
  • Lenses
  • Prisms


Tab.1. Typical specification of CaF2 optical components

Specification Typical State-of-the-art
Sizes See table in the article Plane Windows and Wedged Windows Up to 200 mm
Diameter tolerance, mm +0/-0.25 RFQ
Thickness tolerance, mm +0/-0.25 RFQ
Thickness matching, mm RFQ
Surface quality, scr/dig 60/40 20/10
Surface flatness, λ @ 633nm per inch* 2 1/8
Parallelism (wedge tolerance) 5 arc min 5 arc sec
Coating none protecting

* For “thick” windows: while Diameter/Thickness ratio ≤8

Transmission Spectrum

CaF2 Transmission Spectrum

The measurements were carried out on Perkin Elmer Lambda-35 spectrophotometer and on BrukerVertex-70 Fourier-spectrometer.

Tab.2. Refractive index

λ, µm n λ, µm n
0.19 1.51 2,65 1,42
0.20 1.50 3,90 1,41
0.21 1.49 5,00 1,40
0.22 1.48 5,80 1,39
0.25 1.47 6,20 1,38
0,27 1.46 6,70 1,37
0,33 1.45 7,00 1,36
0,41 1.44 7,50 1,35
0,88 1.43 8,22 1,34

Tab.3. Optical properties

Transmission range, microns 0,15 - 9,0
Colour Colourless
Reflection losses @ 5 µm (2 surfaces), % 5,4
Restrahlen peak, μm 35
dN/dT, 10-6/C -10,6

Tab.4. Physical and mechanical properties

Class / Structure Cubic FCC, Fm3m, (111) cleavage
Density @300K, g/cm3 3.18
Molecular Weight 78.08
Lattice Constant, Å 5.46
Melting Point, °C 1418
Thermal Conductivity @319K, W/(mxK) 9.71
Thermal Expansion @300K, 10-6/C 18.5
Hardness, Knoop with 200 g indenter 158.3 (100)
Specific Heat Capacity, J/(kg×K) 854
Dielectric Constant for 106 Hz @300K 6,76
Young Modulus (E), GPa 75.8
Shear Modulus (G), GPa 33.77
Bulk Modulus (K), GPa 82.71
Elastic Coefficient C11 = 164 C12 = 53, C44 = 33.7 MPa
Apparent Elastic Limit, MPa 36,54
Poisson Ratio 0,26


Tab.5. Chemical stability / Solubility

in water
(at 0оС)
0,0017 g/100 cm3
in acids slightly insoluble
in organic solvents:  
acetone insoluble
lower spirits insoluble
ether insoluble

Please pay your attention that this article is for your information only. We do not supply CaF2 in ingots as well as semi-finished products. Our standard products are polished parts.

For further information on our CaF2 optical components please see the following: Windows for IR-spectroscopy, FTIR Beam Splitter, Packaging or fill in our request form.
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