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Calcium Fluoride (CaF2) Windows


  • UV to IR wavelength range 0.18-8 μm
  • Excellent as the security inspection windows

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Materials IR grade Calcium fluoride crystals Aperture >90%
Dimension Tolerance +0.0/-0.2mm Thickness Tolerance +/-0.1mm
Surface Quality 60/40 S/D Parallelism 1 arc minute
Chamfer 0.3-0.5mmx45degree Coating Optional protective coating

Physical and Optical Properties:

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


Due to its high average transmission and low chromatic aberration relative to other IR materials, calcium fluoride(CaF2 ) is an excellent choice for windows and lenses for spectroscopy applications in the deep UV to near IR wavelength range (180 nm-8 µm). For its good transmission properties at LWIR range, the CaF2 are often selected as the windows for thermal imaging security inspections in electric power facilities and petroleum industries. A protective coated could be made on the windows surface to improve its deliquescence properties. 
Hangzhou Shalom EO provides the crystals optical windows and also the windows assembly with metal holders for thermal imagine inspection applications.

Transmission curve of the CaF2 windows of different thickenss