Optical Crystals

CaF2 crystals have a small chromatic aberration.
When a fluorite lens is made in combination with a common optical glass, the chromatic aberration becomes very small, and it can obtain perfect optical performance with no focal-length difference in the wide wavelength band region.

Our CaF2 crystal can cover the wide wavelength region from ultraviolet to infraredit.
It is widely used for steppers, TV camera lenses, and window material for lasers as optical material.

The technical data of our CaF2 crystals are listed in the world-famous industry standard optics simulation software, OpticStudioTM published by Zemax, LLC.
Moreover, we manufacture and sell other crystal materials such as BaF2 and MgF2.

Transmittance Spectra of CaF2, BaF2, and MgF2

CaF2 Transmittance Spectrum

BaF2 Transmittance Spectrum

Table 1. Physical Properties I

  CaF2 BaF2 MgF2
Abbe Number (Vd) 95.1 81.61 106.22
Transmission Range 180 nm – 10.0 µm 200 nm – 12 µm 200 nm – 5.0 µm
Density 3.18 g/cm3 4.893 g/cm3 3.177 g/cm3
Knoop Hardness 158.3 kg/mm2 82 kg/mm2 415 kg/mm2
Young’s Modulus 75.8 GPa 53.07 GPa 138.5 GPa
Shear Modulus 33.77 GPa 25.4 GPa 54.66 GPa
Bulk Modulus 82.71 GPa 56.4 GPa 101.32 GPa
Poisson’s Ratio 0.26 0.343 0.276
Coefficient of
Thermal Expansion
18.85 x 10-6 /°C 18.4 x 10-6 /°C 13.70 x 10-6 /°C (Parallel)
8.48 x 10-6 /°C (Perpendicular)
Heat Capacity 0.854 J/K 0.41 J/K 1.003 J/K
Melting Point 1418 °C 1368 °C 1255 °C
Change in Index of
Refraction
with
Temperature
(+20/+40°C @ 1060 nm)
-10.6 x 10-6 /°C -15.2 x 10-6 /°C 2.3 x 10-6 /°C
(Parallel)
1.7 x 10-6 /°C
(Perpendicular)
(@400nm)

Table 2. Physical Properties II

    CaF2 BaF2
Solubility in H2O 0℃, g / 100g・H2O 0.008575  
Solubility in H2O g / 100g・H2O 0.00151(18℃) 0.162(30℃)
Acetone Acetone Insoluble  
Melting Point 1418 1280
Specific Heat cal/g・℃ 0.211(50℃) 0.098(27℃)
Thermal Conductivity cal / cm・sec・℃ 0.0241(50℃) 0.028 (13℃)
Molecular Weight   78.08 175.36
Crystal System   Cubic Cubic
Structure   Cubic Cubic
Cleavage Plane   {111} {111}

Table 3. Physical Properties III

    VUV UV Vis/IR
Refractive Index nd 1.43381 1.43385
Internal Transmittance % 0.99~   0.99~
Coefficient of
Linear Expansion
/℃ 2.0×10-5
Young’s Modulus GPa 90
Stress Birefringence nm/cm ~5   ~10(→~5)
Refractive Index
Homogeneity
ppm ~3   ~10

Table 4. Refractive Index

Wavelength, μm CaF2
10.00000    
9.00000    
8.00000   1.349830
7.00000   1.369320
6.00000   1.385590
4.00000   1.409630
3.00000   1.417850
2.32542 n2325 1.422124
2.00000   1.423850
1.97009 n1970 1.424012
1.52958 n1530 1.426127
1.12864 n1130 1.428112
1.01398 nt 1.428800
0.85211 ns 1.430029
0.76819 nA’ 1.430884
0.70652 nr 1.431672
0.65627 nc 1.432459
0.64385 nc’ 1.432680
0.63280 nHe-Ne 1.432886
0.58929 nD 1.433806
0.58756 nd 1.433847
0.54607 ne 1.434935
0.48613 nF 1.437015
0.47999 nF’ 1.437273
0.44157 nHe-Cd 1.439145
0.43583 ng 1.439469
0.40466 nh 1.441489
0.36501 ni 1.444888
0.334244   1.448482
0.289444   1.456168
0.253728   1.465982
0.228872   1.476361
0.214506   1.484561
0.194227   1.500599
0.184950   1.510555

Table 5. Optical Properties

    S-FPL53 CaF2
Refractive Index nd 1.438750 1.433847
ne 1.439854 1.434935
Abbe Number νd 94.93 95.23
νe 94.49 94.70
Dispersion nF-nc 0.004622 0.004556
nF’-nc’ 0.004655 0.004593

Refractive Index of CaF2