CaF₂ Single-Crystal Substrates

Key advantages

• Broad optical transparency from the UV to the infrared
• Low refractive index
• Low optical dispersion
• Low birefringence in suitable optical grades

Properties

Chemical formula

CaF₂

Crystal structure

Cubic, fluorite structure

Space group

Fm-3m (No. 225)

Lattice constant

a ≈ 5.462 Å

Cleavage planes

{111} planes

Density

3.18 g/cm³

Mohs hardness

4

Young's modulus

146.1 GPa along ⟨100⟩; ≈89.9 GPa along ⟨111⟩

Thermal expansion coefficient

16–19 × 10⁻⁶ K⁻¹, depending on temperature

Thermal conductivity

9.71 W/(m·K) at 36 °C

Typical transmission range

0.13–10 µm, grade-dependent

Refractive index

≈1.4289 at 1 µm; ≈1.399 at 5 µm

Transmittance for 2 mm Thickness

The following figure illustrates the spectral transmittance of a 2 mm thick CaF₂ sample. Actual transmission depends on material grade, surface condition, and measurement conditions.

CaF₂ Refractive Index by Wavelength

Wavelength (µm)	Refractive index
0.2	1.4951
0.5	1.4365
1	1.4289
2	1.4239
3	1.4179
4	1.4096
5	1.3990
6	1.3856
7	1.3693
8	1.3498
9	1.3268
10	1.3002
11	1.2676
12	1.2299

Typical applications

• UV and DUV optical systems
• UV, visible, and infrared spectroscopy
• Optical metrology and inspection systems
• Semiconductor optical metrology
• Surface science and thin-film research
• Optical research and laboratory equipment

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Optical Windows

Flat, wedged, tubular, and Brewster window configurations, including chip-free, unchamfered edge options.