Magnesium Fluoride has excellent transmission from 200nm (may even be used as low as 121nm – the hydrogen Lyman –alpha line) to 6μm and has the lowest index of refraction of commonly used IR materials. Magnesium Fluoride optics are an excellent selection for environments where ruggedness are durability are required. Its Knoop hardness (415) is more than twice that of Calcium Fluoride. The grade of magnesium fluoride offered has the C-axis oriented to minimize birefringence, which makes the optics less susceptible to a radiation induced colored center. Magnesium Fluoride is commonly used in thermal imaging and excimer laser applications.antireflective coating.
| Specification | |
| Transmission Range | 0.121µm to 7.0µm |
| Density | 3.177 g/cm3 |
| Thermal Expansion | 13.7 x 10-6 /°C Parallel to C-axis |
| Co-Efficient | 8.48 x 10-6 /°C Perpendicular to C-axis |
| Surface Quality | Polishes of 20-10 scratch-dig are achieved at extra costs respectively mainly for UV applications. Typical specifications for surface quality in the visible & near infrared regions are a 40-20 & 60-40 scratch dig in the 3 to 7µm range. MgF2 is diamond turnable. |
| Surface Accuracy | In the UV & Visible spectral regions, surface figure ranges from 1/10 wave to 1/2 wave @ 0.6328µm. In the infrared, typical required surface figure ranges from 1/2 wave to 2 waves @ 0.6328µm & are specified depending on the system performance requirements. |
| AR Coating Options | Magnesium Fluoride can be AR coated for use in the infrared but generally without much improvement in transmission due to its low index of refraction & already high transmission. |
| Typical Applications | Thermal imaging, Astronomical, Excimer laser applications. |
| Wavelength (µm) | Index of Refraction (n) |
| 0.114 | 1.7805 |
| 0.118 | 1.68 |
| 0.13 | 1.556 |
| 0.15 | 1.48 |
| 0.17 | 1.447 |
| 0.19 | 1.431 |
| 0.3 | 1.4 |
| 0.7 | 1.376 |
