Specifications:
| Materials | CaF2 crystals | Diameter Range | ~200mm |
| Diameter Tolerance | +0.0/-0.2mm | Thickness Tolerance | +/-0.1mm |
| Surface Quality | 60/40 S/D | Fringes (N) | 3 |
| Irregularity (delta N) | 1 | Centration | 3' |
| Chamfer | 0.1-0.3mmx45 degree | Coatings | AR/AR@3-5micro |
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 | 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 between 0.25μm and 7μm and low chromatic dispersion relative to other IR materials, calcium fluoride (or CaF2) is an excellent choice for windows and lenses for spectroscope in the deep UV to MWIR wavelength range. For its good transmission properties at the MWIR range, CaF2 lenses are often selected as the lens for MWIR (3-5 micro) thermal imaging applications. Other attributes of CaF2 lenses include high damage thresholds and low absorption, which make them popular for excimer lasers. Its Group Velocity Dispersion (GVD) is the lowest among the IR transmitters, therefore CaF2 is also recommendable for Femtosecond IR lasers. In addition, CaF2 lenses also boast chemical inertness and excellent mechanical strength.
Curves:
Transmission curves of CaF2 substrates of different thicknesses
