MgF2birefringenta

Magnesium fluoride (MgF2) is a transparent, uniaxial birefringent crystal widely used in optical applications. It crystallizes in a tetragonal rutile-type structure, and its optical anisotropy leads to two principal refractive indices for light polarized along different directions. This birefringence, while modest, is stable across a broad spectral range and can be exploited in polarization-control devices.

In MgF2, light splits into ordinary (n_o) and extraordinary (n_e) rays, with the birefringence defined as Δn = n_e − n_o. The difference is small and wavelength dependent, but sufficient for precise control of polarization. MgF2 remains transparent from the vacuum ultraviolet through the visible and into the infrared, offering low absorption, low scattering, and good laser-damage resistance, which makes it valuable for high-performance optics.

Applications of MgF2 birefringence include waveplates (quarter-wave and half-wave plates) and polarizers used in UV, visible, and near-infrared systems. It is also employed in UV-compatible windows and coatings, spectroscopic instruments, and astronomical optics, where broad transmission and stable birefringence are important. The material’s wide transmission range and optical quality contribute to its role in specialized polarization optics and UV instrumentation.

Manufacture and handling: high-purity MgF2 single crystals are grown by standard methods such as the Czochralski process. Surfaces are precision-polished to optical quality, and the crystals are cut with awareness of the optical axis. MgF2 is chemically stable and mechanically robust, with dispersion data typically modeled by Sellmeier-type equations to design wavelength-specific components.