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.
Capabilities:
| 1) | Diameter : max 30~40mm |
 Calcite: T% vs Wavelength |
| 2) | Length: max 25~35mm | |
| 3) | Surface Quality: better than 20/10 scratch/dig Per MIL-0-13830A | |
| 4) | Beam Deviation: <3 arc minutes | |
| 5) | Optical Axis Orientation: +/-0.5¡ã | |
| 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.
| Physical and Optical Properties: |
| Transparency Range | 350~2300nm |
| Partical Shape | Crystalline rhombihedral |
| Density | 2.7 g/cm 3 |
| 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(¦¤=ne-no) and walk-off angle at 45¡ãC (¦Ñ) | n o =1.6557, n e =1.4852 ¦¤n=-0.1705, ¦Ñ= 6.20¡ã @ 630nm |
| n o =1.6629, n e =1.4885 ¦¤n =-0.1705, ¦Ñ= 6.20¡ã @ 1300nm |
|
| Sellmeier Equation | n o 2 =2.69705+0.0192064/(¦Ë 2 -0.01820)-0.0151624¦Ë 2 n e 2 =2.18438+0.0087309/(¦Ë 2 -0.01018)-0.0024411¦Ë 2 |
Note:Please refer to Page II-23 for more information about Calcite Polarizers.