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Birefringent Crystals
Calcite
Calcite is a natural crystal that has high birefringence, wide spectral transmission and availability in reasonably sized rhombs. It's a negative uniaxial crystals and mostly used as visible and near IR polarizers.
| Physical and Optical Properties | |
|---|---|
| Transparency Range | 350~2300nm |
| Partical Shape | Crystalline rhombihedral |
| Density | 2.7 g/cm3 |
| Hygroscopic Susceptibility | Low susceptibility to moisture |
| Mohs Hardness | 3 |
| Thermal Expansion Coefficient | a a=24.39x10 -6 /k; a c=5.68x10 -6 /k |
| Crystal Class | Negative uniaxial with no=na=nb, ne=nc |
| Refractive index, birefringence(Δ=ne-no) and walk-off angle at 45°C (ρ) | n o =1.6557, n e =1.4852 Δn=-0.1705, ρ= 6.20°@ 630nm |
| n o =1.6629, n e =1.4885 Δn =-0.1705, ρ= 6.20°@ 1300nm |
|
| Sellmeier Equation | n o 2 =2.69705+0.0192064/(λ2 -0.01820)-0.0151624λ2 n e 2 =2.18438+0.0087309/(λ2 -0.01018)-0.0024411λ2 |
Capabilities:
1) Diameter : max 30~40mm
2) Length: max 25~35mm
3) Surface Quality: better than 20/10 scratch/dig Per MIL-0-13830A
4) Beam Deviation: <3 arc min
5) Optical Axis Orientation: +/-0.5°
6) Flatness: <l /4 @633nm
7) Transimission Wavfront Distortion: < l /2 @633nm
8) Coating: upon customer's specification
Notes
As the susceptibility is low so that it's easy to moisture,it's difficult to achieve excellent optical quality due to low hardness.
Note:Please click here for more detail about Calcite Polarizers.