Alfa Chemistry uses a low refractive index crystalline material, potassium chloride (KCl), to customize infrared optical elements that are commonly used as sputtering windows in CO2 lasers. Due to its broad transmission band, it can be used optically in the UV, visible, mid-wave, and far-infrared ranges. All custom KCl 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 for your customer service as soon as possible!
Our Services
Alfa Chemistry can provide a wide range of custom KCl optics, including windows and grits, that can be manufactured to your specific requirements. We can provide both coated and uncoated optical options, such as broadband anti-reflective coatings. The table below lists our typical manufacturing requirements. If your needs are not covered here, please get in touch with our technical sales team. We have years of experience in this industry and are always working to improve our skills.
KCl Windows
| Diameter Range | 5 mm ~ 80 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 80 mm |
| Linear Tolerance | ± 0.1 mm |
| Angular Tolerance | 5 arc minutes |
| Edge Finish | ground, blacked |
| Chamfer | 0.3x0.3@45° |
| Surface Quality | 40-20 scratch/ dig |
KCl Prisms
| Length of Hypotenuse | up-to 80 ± 0.1 mm |
| Length of Sides | up-to 80 ± 0.1 mm |
| Thickness | 30 ± 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 | 40-20 scratch/dig |
KCl Ground Blanks
| Diameter range | less than 5 mm to 80 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 80 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° |
KCl Spherical Lens
| Focal Length | up-to 5000 ± 0.1mm or 1% whichever largest |
| Back Focal Length | up-to 5000 ± 0.1mm or 1% of focal length |
| Radius of Curvature, S1/S2 | up-to 5000 ± 1 fringe across surface |
| Form Error, S1/S2 | better than λ/4 (633nm) over aperture |
| Centration (Arc Second) | less than 60 |
| Centre Thickness | up-to 50 ± 0.1mm |
| Edge Thickness | minimum 1mm or 1% of centre thickness |
| Length/Width of Aperture | up-to 80 ± 0.1mm |
| Diameter | 80 ± 0.1mm |
| Clear Aperture | 90% of diameter |
| Edge Finish | blacked, ground |
| Chamfer | 0.3x0.3@45° |
| Surface Quality | 40-20 scratch/ dig |
Applications:
- Laser Windows: As a disposable protective window in CO2 laser systems, KCl is frequently employed because of its low refractive index, low absorption, and high damage threshold.
KCl's Optical Properties
KCl is a commonly used material in FTIR spectroscopy. In IR spectroscopy, KCl is used as windows, lens, and prism when transmission between 0.3 and 20 µm is necessary. Although it is slightly more durable than potassium bromide, it does not transmit infrared light as far. Because KCl is so delicate, it must be handled carefully. Since KCl is water soluble, polished surfaces should either be shielded from moisture exposure or have a protective coating put to them.
Fig 1. Optical absorption spectra of KCl single crystal (a) and Eg of pure KCl (b). (Bouhdjer L, et al. 2014)
The optical characteristics of KCl are briefly described here.
| Transmission Range | 0.21 to 20 µm |
| Refractive Index | 1.45644@10 µm |
| Melting Point | 776 °C |
| Density | 1.99 g/cm3 |
| Hardness | Knoop 7.2 <110>, 9.3 <100> with 200g indenter |
If you need technical advice, please contact our technical team to learn more about our high-quality services.
Reference
- Bouhdjer L, et al. (2014). "Structural and Optical Properties of CdSe Doped KCl Single Crystal." Journal of New Technology and Materials. 2(1): 34-37.