CaF2/MgF2 Window
| Machinable shape | Circle, rectangle, polygon and other shapes |
| Size range | Diameter (maximum diagonal)：Φ8-Φ80mm |
| Thickness：0.05-50mm | |
| Facial type | Reflected PV better than 1/4 λ， Transmission PV is better than 1/10 λ |
| Fineness | 10-5 20-10 40-20 |
| Surface roughness | <5nm |
| Parallelism | <20″ |
| Coating | Customized according to customer requirements |
GaF2 and MgF2 crystals have high hardness, strong resistance to mechanical shock and thermal shock, and good transmissivity in ultraviolet, light and infrared bands. They are widely used in laser, infrared optics, ultraviolet optics, high-energy detectors and other fields, especially their optical performance in ultraviolet band is very good. They are known as optical crystals in the ultraviolet cut-off band, with high transmissivity and small fluorescence radiation, It is an ideal material for ultraviolet photodetectors, ultraviolet lasers and ultraviolet optical systems. Different from GaF2, MgF2 is a birefringent crystal.
Physical Properties
| CaF2 | MgF2 | |
| Density（g/cm3） | 3.18 | 3.177 |
| Melting point（℃） （℃） | 1360 | 1255 |
| Dielectric constant | 6.76@1HMZ | 4.87@1HMZ（Parallel C-axis） 5.44@1HMZ（Vertical C-axis） |
| Purity（%） | 99.9996 | 99.9996 |
| Coefficient of thermal expansion（1/℃） | 18.85*10^-6 | 13.7*10^-6（Parallel C-axis） 8.48*10^-6（Vertical C-axis） |
| 7.3*10^-6@373K | 7.0*10^-6@373K | |
| Thermal conductivity（J/k.m.s） | 9.71 | 0.3@27℃ |
| Heat capacity（J/g.k） | 0.854 | 1.003@298K |
| Hardness (knoop) (kg/mm2) | 158.3 | 415 |
| Shear modulus （GPa） | 33.77 | 15.66 |
| Young’s modulus (GPa) | 75.8 | 138.5 |
| Poisson's ratio | 0.26 | 0.276 |
Optical Properties
| CaF2 | MgF2 | |
| Through wavelength range | 130nm-10000nm | 110nm-7500nm |
| Refractive index inhomogeneity （ΔN/N） | ＜3*10^-6@632.8nm | |
| Reflection loss （2 sides） | 5.4%@5000nm | 11.2%@120nm |
| 5.1%@1000nm | ||
| Thermo-optic coefficient dn/dT（1/℃） | -10.6*10^-6 | 2.3*10^-6@400mnm |
Change of refractive index with wavelength
| CaF2 | |||
| Wavelength (nm) | Refractive index (n) | Wavelength (nm) | Refractive index (n) |
| 190 | 1.51 | 2650 | 1.42 |
| 210 | 1.49 | 3900 | 1.41 |
| 250 | 1.47 | 5000 | 1.40 |
| 330 | 1.45 | 6200 | 1.38 |
| 410 | 1.44 | 7000 | 1.36 |
| 880 | 1.43 | 8220 | 1.34 |
| MgF2 | ||
| Wavelength (nm) | Refractive index 1 (n) | Refractive index 2 (n) |
| 200 | 1.42 | 1.43 |
| 230 | 1.41 | 1.42 |
| 270 | 1.40 | 1.41 |
| 340 | 1.39 | 1.40 |
| 560 | 1.38 | 1.39 |
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