Lithium Fluoride (LiF) is a wide-bandgap ionic crystal renowned for the deepest UV transmission among common optical materials. Its combination of low refractive index and excellent radiation resistance has made it a staple for VUV optics and high-energy diagnostics.
Material Overview
LiF crystallizes in the rock-salt (NaCl) structure with strong ionic bonding, yielding a large bandgap and transmission that reaches the Lyman-α line at 121 nm. The refractive index is low in the visible, and the material maintains transparency under extreme thermo-mechanical loading, with modern studies mapping its index behavior under dynamic compression to hundreds of gigapascals. Thermal conductivity at room temperature is moderate for a halide, supporting thermal management in compact optics.
Applications and Advantages
LiF excels in VUV windows, prisms, and spectroscopic components where minimal absorption is critical. Its lattice spacing also makes LiF a useful crystal in X-ray monochromators and analyzers. In high-energy physics and shock diagnostics, LiF windows are favored for their predictable elasto-optic response, enabling accurate interferometric and velocimetry measurements during ramp or shock loading. The material’s radiation tolerance and optical homogeneity further recommend it for spaceborne instrumentation.
Goodfellow Availability
Goodfellow supplies lithium fluoride with options for custom dimensions to integrate into beamlines, monochromators, or VUV benches. Our team can discuss machining allowances and polishing requirements for your optical path.
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References
- Hawreliak, J. A., et al. (2024). Refractive index of lithium fluoride at high dynamic stresses. Physical Review B. https://link.aps.org/doi/10.1103/PhysRevB.110.134106
- Crystran Ltd. (n.d.). Lithium Fluoride (LiF)—Optical material data. https://www.crystran.com/optical-materials/lithium-fluoride-lif
- Kurosawa, S., et al. (2014). Growth and optical properties of LiF/LaF3 eutectic crystals. Radiation Measurements. https://www.sciencedirect.com/science/article/abs/pii/S0955221914000727