Fluoride crystals feature wide transmission range from deep UV to far infrared, are widely used for optical windows, lenses, beam-splitters and prisms. Because of the low absorption and low refractive index, Fluoride crystals can work well without anti-reflection coating. LNG Optics offer following elements for application of high power UV lasers.
Main properties of Fluoride crystals:
Chemical Formula |
CaF2 |
BaF2 |
LiF |
MgF2 |
Transmission Range (μm) |
0.13 – 10.0 |
0.15 – 12.0 |
0.12 – 6.0 |
0.12 – 7.0 |
Refractive index |
1.6921 - 1.3161 |
1.678 - 1.376 |
1.624 – 1.298 |
no 1.628 - 1.314 |
Δn/ΔT (10-6/℃) |
-10.6 |
-15.2 |
- 16.0 |
⊥c 1.7, ∥c 2.3 |
Crystal Structure |
Cubic |
Cubic |
Cubic |
Tetragonal |
Lattice Parameters (Å) |
5.462 |
6.196 |
4.026 |
a=4.64, c=3.06 |
Cleavage plane |
<111> |
<111> |
<100> |
<110> or <100> |
Melting Point (℃) |
1360 |
1280 |
870 |
1255 |
Knoop hardness (kg/mm²) |
158.3 (100g indenter) |
82 (500g indenter) |
102 (600g indenter) |
415 (500g indenter) |
Density (gram/cm3 ) |
3.18 |
4.89 |
2.64 |
3.18 |
Thermal Conductivity (W/m/K) |
9.71 |
11.72 |
4.01 |
⊥c 31.6, ∥c 21.0 |
Thermal Expansion coef. (10-6/K) |
18.8 |
18.1 |
37.0 |
⊥c 8.5, ∥c 13.7 |
Young’s Modulus (GPa) |
75.80 |
53.07 |
64.97 |
⊥c 79.7, ∥c 169.1 |
Solubility in 100g water @ 20℃ |
0.0017 |
0.0017 |
0.27 |
0.0002 |
Windows, Lenses, Beam-splitters and Prisms.
|
CaF2 |
BaF2 |
LiF |
MgF2 |
Warranted transmittance |
4mm T≥90% @ 193nm |
4mm T≥90% @ 266nm |
4mm T≥95% @ 193nm |
4mm T≥90% @ 193nm |
Surface quality (Scratch-Dig) |
40/20 to 20/10 |
20/10 |
40/20 |
20/10 to 10/5 |
Surface flatness @ 633nm |
λ/10 to λ/4 |
λ/10 to λ/4 |
λ/4 to λ/2 |
λ/10 to λ/4 |
Clear Aperture |
90% |
90% |
85% |
90% |