Calcium Fluoride (CaF2)
Calcium Fluoride has widespread IR application as spectroscopic CaF2 windows, CaF2 prisms and CaF2 lenses. Especially pure grades of Calcium Fluoride (CaF2) find useful application in the UV and as UV Excimer laser windows. Calcium Fluoride (CaF2) is available doped with Europium as a gamma-ray scintillator.
 
Product Data -----------------------------------------------------
 
Transmission Range : 0.13 to 10 μm
Refractive Index : 1.39908 at 5 μm (1) (2)
Reflection Loss : 5.4% at 5 μm
Absorption Coefficient : 7.8 x 10-4 cm-1 @ 2.7 μm
Reststrahlen Peak : 35 μm
dn/dT : -10.6 x 10-6/°C (3)
dn/dμ = 0 : 1.7 μm
Density : 3.18 g/cc
Melting Point : 1360°C
Thermal Conductivity : 9.71 W m-1 K-1 (4)
Thermal Expansion : 18.85 x 10-6/°C (5)(6)
Hardness : Knoop 158.3 (100) with 500g indenter
Specific Heat Capacity : 854 J Kg-1 K-1
Dielectric Constant : 6.76 at 1MHz (7)
Youngs Modulus (E) : 75.8 GPa (7)
Shear Modulus (G) : 33.77 GPa (7)
Bulk Modulus (K) : 82.71 GPa (7)
Elastic Coefficients : C11 = 164 C12 = 53 C44 = 33.7 (7)
Apparent Elastic Limit : 36.54 MPa
Poisson Ratio : 0.26
Solubility : 0.0017g/100g water at 20°C
Molecular Weight : 78.08
Class/Structure : Cubic (111) cleavage
 
Refractive Index and Optical Transmittance curve----
Refractive Index(No = Ordinary Ray):
µm    No µm    No µm    No
0.149    1.5800 0.161    1.5490 0.195    1.5000
0.200    1.4950 0.222    1.4800 0.248    1.4680
0.266    1.4621 0.280    1.4584 0.300    1.454
0.337    1.4481 0.400    1.4419 0.486    1.4370
0.588    1.4339 0.656    1.4325 0.687    1.4320
0.728    1.4314 0.884    1.4298 1.014    1.4288
1.100    1.4283 1.250    1.4275 1.650    1.4256
1.900    1.4244 2.058    1.4236 2.450    1.4214
2.700    1.4199 2.800    1.4192 3.050    1.4175
3.400    1.4149 4.000    1.4096 4.400    1.4057
4.800    1.4014 5.000    1.3991 5.304    1.3952
5.893    1.3871 6.483    1.3782 7.072    1.3681
7.661    1.357 8.251    1.3444 8.840    1.3308
9.429    1.3161
Optical Transmittance Curve of CaF2 (Reference Data):
calcium-fluoride-caf2 Transmittance
 
Special properties of CaF2-----------------------------------

CaF2 is used in the UV,VIS,NIR and/ or the MW spectral regions.

It is about twice as hard as BaF2

CaF2 is less susceptible to thermal shock than BaF2

CaF2 does not degrade due to moisture under ambient atmospheric conditions.

CaF2 is less expensive than BaF2.

CaF2 is more readily available in large sizes than BaF2.

CaF2 is diamond turnable.

Typeical application: Cryogenically cooled thermal imaging, Astronomical, Microlithography, Excimer Laser applications.

Products manufactured: Lenses, Aspheric lenses, windows, Optical Beamsplitters, Optical Filters, Wedges, Prisms.

Surface finish: Polishes of 20-10 scratch-dig are mostly specified for use in UV and visible applications. Typical specifications for surface quality in the infrared are a 40-20 scratch dig in the 0.75 to 3μm spectral region and 60-40 scratch-dig for the 3-7μm area.

Surface figure: Surface figure: In the UV and Visible spectral regions, surface figure ranges from 1/10 wave to 1/4 wave @ 0.6328μm. In the infrared, typical required surface figure ranges from 1/4 wave to 2 waves @ 0.6328 μm and are specified depending on the system performance requirements.

AR coating options: Available coatings for CaF2 include BBAR for 0.8 to 2.5μm, 3 to 5μm or the 1 to 5μm spectral regions
Product Notes:------------ --------------------------------------

Calcium fluoride (CaF2 or fluorite) is grown by vacuum Stockbarger technique in diameters of up to about 250mm. Material for Infrared use is grown using naturally mined fluorite, in large quantities at a relatively low cost. For UV applications chemically prepared raw material is generally used. For Excimer applications, we use only the highest grade of specially selected material and crystal.

REFERENCES:
(1) Handbook Optical Constants, ed Palik, V2, ISBN 0-12-544422-2
(2) Dressler et al., Cryst.Res.Technol. V27, p413, 1992
(3) I.H.Malitson; J.Opt.Soc.Am. Vol52, p1377, 1962
(4) Ballard et al; Rev. Sci. Instr., V21, p905, 1950
(5) Batchelder & Simmons, J.Chem. Phys. V41, p2324 N8 1964
(6) Schumann & Neumann, Crys. Res. Tech V19, 1984
(7) Dickinson, IR laser windows, AFCRL-TR-0318, Air Force, Cambridge 1975

Data provided is extracted from our technical handbook of materials. While every attempt has been made to verify the source of the information, ultiQuest Technology accept no responsibility for accuracy of data

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