An optical coating is a vital component of a optical component or assembly that is created to improve or decrease the reflectance, transmittance, or polarization properties of an optical component. Coatings can be made from one or more layers of dielectric, IR, or metallic materials.
Alfa Chemistry has the knowledge and experience in optical coatings to satisfy our clients' shifting demands for reliable optical coatings. Each unique coating is created for a particular wavelength or range of wavelengths. In order to improve designs for client applications, our experts are continually investigating the performance characteristics of novel coating materials.
Coating Design
The structure of the coating, the number of layers, the material's refractive index, and the optical characteristics of the substrate all affect the spectrum performance and other crucial characteristics of optical films. Most coatings have a structure that is composed of distinct layers of high and low refractive index materials that alternate. Different types of coatings are produced by different stacking configurations of structures. To get the best performance characteristics in the targeted wavelength range, layer thickness and refractive index are fine-tuned. Alfa Chemistry has a variety of thin film modeling tools for planning, describing, and improving various aspects of the performance of specific coatings.
Comprehensive Optical Coating Technology
- Electron Beam and Thermal Evaporation
The most widely used techniques for creating thin films are heat evaporation and electron beam because they are straightforward and reasonably inexpensive. We use thermal evaporation to deposit metals and dielectrics that are less compatible with electron beam coatings.
For many compatible materials, electron beam technology provides coatings with lower stresses where surface flatness is a priority, higher laser-induced damage thresholds (LIDT), and improved control of impurities in the deposited material. We use an electron beam source to evaporate selected materials such as transition metal oxides (eg, TiO2, Ta2O5, HfO2, Nb2O5, ZrO2), metal halides (MgF2, YF3), or SiO2. Electron beams are particularly suitable for coating components operating at deep UV and IR wavelengths.
Fig 1. Schematic diagram showing thermal evaporation. (Pujahari R. M, et al. 2021)
- Ion Assisted Deposition (IAD)
IAD coatings can deposit robust coatings with very high laser-induced damage thresholds (LIDT) and very low thermal shifts. Additionally, the pre-cleaning or etching of substrate surfaces using ion beams can help with film adherence. IAD coatings outperform films created only by electron beam evaporation in terms of mechanical endurance, environmental stability, and scattering.
- Ion Beam Sputtering (IBS)
IBS coatings are produced in a vacuum chamber. IBS creates a highly hard, thick coating that is ideal for applications requiring very high reflection and little loss. IBS is, therefore, a good choice for finishing very polished mirrors.
| Deposition Technology | Coating Types |
|---|---|
| Thermal evaporation | Metallic coating |
| e-beam | High-reflection / Anti-reflection / V-coats, double-V coats / Broadband Anti-reflection |
| IAD | High-reflection / Anti-reflection / V-coats, double-V coats / Broadband Anti-reflection / Bandpass filters |
| IBS | Dielectric mirrors / High-reflection |
Note: Every one of these methods has certain benefits and restrictions of its own. To discuss the technology that best satisfies your needs get in touch with us.
If you need technical advice, please contact our technical team to learn more about our high-quality services.
Reference
- Pujahari R. M, et al. (2021). "Solar Cell Technology." Energy Materials. Fundamentals to Applications: 27-60.