Alfa Chemistry customizes infrared optical components using calcite (CaCO3) optics, a strongly birefringent material used in polarizers and phase difference plates. All custom calcite optics are rigorously tested by skilled experts at cutting-edge metrology facilities, giving customers the peace of mind that their needs will be met. Contact us as soon as possible to provide you with customer service!
Our Services
Alfa Chemistry offers a range of quality custom calcite optics, including calcite polarizers and windows, calcite lenses, calcite prisms and calcite polarizers, with custom parts that can be tailored to your specifications for a range of applications. The table that follows lists our typical manufacturing requirements. Our skills are constantly growing, so if your need is not covered above, please get in touch with our technical sales team, who will be able to help you out because we have years of experience in this area.
Calcite Windows
The most commonly requested specifications for an calcite window are as follows:
| Diameter Range | 5 mm ~ 50 mm |
| Diameter Tolerance | ± 0.1 mm |
| Centre Thickness | up to 30 mm |
| Centre Thickness Tolerance | ± 0.05 mm |
| Clear Aperture | 90% |
| Centration Tolerance | 1 arc minute |
| Form Error | better than λ/4 (633nm) over aperture |
| Surface Radius Tolerance | 1 fringe over aperture |
| Linear Dimension | up to 50 mm |
| Linear Tolerance | ± 0.1 mm |
| Angular Tolerance | 5 arc minutes |
| Edge Finish | ground, blacked |
| Chamfer | 0.3x0.3@45° |
| Surface Quality | 20-10 scratch/dig |
Calcite Prisms and Polarisers
The most commonly requested specifications for the calcite prisms and polarisers are as follow:
| Length of Hypotenuse | up-to 50 ± 0.1 mm |
| Length of Sides | up-to 50 ± 0.1 mm |
| Thickness | 20 ± 0.05 mm |
| Angle Tolerance | better than 1 arc minute |
| Edge Finish | ground, blacked |
| Clear Aperture | 90% of entrance dimensions |
| Chamfer | 0.3x0.3@45° |
| Form Error | 0.2 fringe from test flat |
| Surface Quality | 20-10 scratch/dig |
Calcite Ground Blanks
The most common specifications for calcite ground blanks are as follows.
| Diameter Range | less than 5 mm to 50 mm |
| Diameter Tolerance | better than ± 0.5 mm |
| Centre Thickness | up to 30 mm |
| Centre Thickness Tolerance | better than ± 0.5 mm |
| Clear Aperture | 90% |
| Linear Dimension | up to 50 mm |
| Linear Tolerance | better than ± 0.5 mm |
| Angular Tolerance | better than 10 arc minutes |
| Edge Finish | fine ground N6 |
| Chamfer | 0.3x0.3@45° |
Applications:
- Polarizing prisms (laser applications)
Calcite can be highly polished to 20/10 scratches or excavations on both the input and output surfaces to reduce any scattering because of its transparency and strong visible-NIR birefringence. Additionally, it has a high damage threshold and a surface output that exhibits unusually high polarization purity.
Common polarization prisms include Rochon, Glan-Taylor/-Glan-Thompson/Glan-laser, and Wollaston prisms.
- Waveplates
Calcite can be used to make wave sheets to alter the polarization state of incident light because it is a birefringent material.
Calcite's Optical Properties
Calcite is an anisotropic crystal and is one of the available birefringent materials. A substance has two separate refractive indices if it is birefringent. This occurs when a non-polarized beam enters the material's input surface and splits into the ordinary (o) and anomalous (e) waves of polarization. The object appears twofold when viewed through a piece of transparent calcite due to its extreme birefringence. At about 590 nm, calcite has an o- and e-ray refractive index of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the o- and e-ray refractive index varies roughly between 1.9 and 1.5, while the e-ray refractive index varies between 1.6 and 1.4.
Fig 1. The experimental and computed values of refractive index vs. wavelength for calcite crysta. (Ghosh G, et al. 1999)
Calcite has a transmittance of over 75% in the 0.3 to 2.3 µm range, making it ideal for visible and NIR applications. The optical characteristics of calcite are briefly described here.
| Transmission Range | 0.3 to 2.3 µm |
| Refractive Index | 1.6654@0.51 µm |
| Melting Point | Decomposes at 825 ℃ |
| Density | 2.71 g/cm3 |
| Hardness | Knoop 155 Mohs 3 |
If you need technical advice, please contact our technical team to learn more about our high-quality services.
Reference
- Ghosh G, et al. (1999). "Dispersion-Equation Coefficients for The Refractive Index and Birefringence of Calcite and Quartz Crystals." Optics Communications. 163(1-3): 95-102.