Calcite
Calcite,
or Iceland Spar is is often mined naturally 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.
Transmission Range : 0.3 to 2.3 µm
Refractive Index : No 1.6654 at 0.51 µm
Reflection Loss : 11.7% at 0.51 µm (2 surfaces)
Absorption Coefficient : n/a
Reststrahlen Peak : n/a
dn/dT : 3 (para) 13 (perp) x 10-6 /°C at 0.5 micron
dn/dµ = 0 : n/a
Density : 2.71 g/cc
Melting Point : 825°C (Decomposes)
Thermal Conductivity : 5.526 (para) 4.646 (perp) W m-1 K-1 at 273K
Thermal Expansion : 25 (para) 5.8 (perp) x 10-6 /°C at 273K
Hardness : Knoop 155 Moh 3
Specific Heat Capacity : 852 J Kg-1 K-1
Dielectric Constant : 8 (para) 8.5 (perp) at 10kHz at 293K
Youngs Modulus (E) : 72.35 (perp) 88.19 (para) GPa
Shear Modulus (G) : 35 GPa
Bulk Modulus (K) : 129.53 GPa
Elastic Coefficients : C11=137; C12=45; C13=45; C14=(21); C33=79
Apparent Elastic Limit : 4.83 MPa (700 psi)
Poisson Ratio : n/a
Solubility : 0.0014g/100g water at 25°C
Molecular Weight : 100.09
Class/Structure : Trigonal (hex), R3c, (1011) cleavage
Refractive Index
µm No Ne µm No Ne µm No Ne
0.20 1.9028 1.5765 0.30 1.7196 1.5137 0.41 1.6801 1.4954
0.51 1.6653 1.4896 0.64 1.6550 1.4849 0.71 1.6521 1.4835
0.80 1.6487 1.4822 0.91 1.6458 1.4810 1.04 1.6428 1.4799
1.50 1.6346 1.4774 1.91 1.627 1.4757 2.10 1.622 1.4749
General Specifications
1) Diameter: 50mm max
2) Length: 35mm max
3) Surface Quality: better than 20/10 scratch/dig Per MIL-0-13830A
4) Beam Deviation: < 3 arc min
5) Optical Axis Orientation: +/- 0.5deg.
6) Flatness: < 1/8 @633nm
7) Transimission Wavfront Distortion: < 1/4 @633nm
8) Coating: upon customer's specification
Notes:
Calcite crystal is difficult to polish due to low hardness, low susceptibility
and easy to moisture. YVO4 or a-BBO crystal is an alternative where high
quality elment is request.
