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Material CaF2
Calcium Fluoride is used for optical windows, lenses and prisms in the 0.15 μm - 9 μm (ultraviolet to infrared) regions. The low power absorption has made this material attached to wide use in high power laser optics. Polished surfaces are stable and will last several years under normal conditions. Due to its composition, CaF2 has a much longer usable lifetime than most materials operating in fluorine environments.
Calcium Fluoride, which is grown by vacuum Stockbarger technique, has a low refractive index, hence can be used without anti-reflection coating. Material for IR use is grown using naturally mined fluorite, in large quantities at relatively low cost. Maximum available size: 380 mm Dia x 70 mm Thk.
| BASE PROPERTIES | |
|---|---|
| PARAMETER | VALUE |
| OPTICAL | |
| Transmission Range | 0.11 to 7.5 microns |
| Refractive Index | N0=1.3836 Ne=1.3957 at 0.405 microns |
| Reflection Loss | 11.2% at 0.12 microns (2 surfaces) |
| Restrahlen Peak | 20 microns |
| dN/dT | +2.3 and +1.7 x 10-6e/ °C at 0.4 microns |
| PHYSICAL | |
| Density | 3.177 g/cm3 |
| Melting Point | 1255 °C |
| Thermal Conductivity | 0.3 W/(m K) at 27 °C |
| Thermal Expansion | 13.7and 8.48 x 10-6e/ °C |
| Hardness | Knoop 415 kg/mm2 |
| Specific Heat Capacity, cal/(g K) at 298 K at 1700 K |
0.24 0.362 |
| Dielectric Constant | 4.87 parallel and 5.45 perpendicular |
| Young's Modulus (E) | 138.5 GPa |
| Shear Modulus (G) | 54.66 GPa |
| Bulk Modulus (K) | 101.32 GPa |
| Elastic Coefficients | C11=140.2 C12=89.5 C44=56.8 C33=204.7 C13=62.9 C66=95.7 |
| Apparent Elastic Limit | 49.64 MPa |
| Poisson Ratio | 0.276 |
| CHEMICAL | |
| Solubility | <0.0002 g/100g water at 0 °C |
| Molecular Weight | 62.32 |
| Class/Structure | Tetragonal, can cleave on C-axis |
| REFRACTIVE INDEX | |||||
|---|---|---|---|---|---|
| Wavelength, μm | 0.20 | 0.23 | 0.27 | 0.34 | 0.56 |
| Refractive Index (ne) | 1.43 | 1.42 | 1.41 | 1.40 | 1.39 |
| Refractive Index (no) | 1.42 | 1.41 | 1.40 | 1.39 | 1.38 |
MgF2 Curve