Optical Coatings  Manufacturers, Traders, Suppliers

Optical coatings are used to enhance the transmission, reflection, or polarization properties of an optical component. For example, about 4% of incident light will be reflected at each surface of an uncoated glass component. An anti-reflection coating could be applied to reduce the reflection at each surface to less than 0.1% and a highly reflective dielectric coating could also be applied to increase reflectivity to more than 99.99%. An optical coating is composed of a combination of thin layers of materials such as oxides, metals, or rare earth materials. The performance of an optical coating is dependent on the number of layers, their thickness, and the refractive index difference between them. This application note discusses optical coating theory, different types of common coatings, and coating manufacturing methods.
Thin film optical coatings are typically created by depositing dielectric and metallic materials, such as tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3), or hafnium oxide (HfO2), in alternating thin layers. In order to maximize or minimize interference, they are typically λ/4 optical thickness (QWOT) or λ/2 optical thickness (HWOT) of the wavelength of the light used in the application. These thin film layers alternate between high index of refraction and low index of refraction, thereby inducing the interference effects needed.
Optical coatings are designed to enhance the performance of an optical component for a specific angle of incidence and polarization of light such as s-polarization, p-polarization, or random polarization. Using the coating at a different angle of incidence or polarization than what it is designed for will result in a significant degradation in performance. Sufficiently large deviations in incidence angle and polarization can result in a complete loss of coating function.

Optical coating
Item Single AR coating, BBAR coating, HR coating, filter coating
Material BK7, Fused Silica, CaF2
Design Wavelength Customer design
Dimension Tolerance +0/-0.05mm
Thickness Tolerance +/-0.1mm
Surface quality 40-20 or better
Surface Figure Cyl surface: lambda/2 or [email protected]
Center Error ETV better than 0.01mm
Clear Aperture 90% of Diameter
Bevel Protective bevel
Coating customer design

Subject coverage: All aspects of classical optical phenomena.
Topics covered include (but are not restricted to): propagation, scattering,
and diffraction; linear and non-linear phenomena; spectroscopy and interferometry;
instrumentation design and testing; thin films; optical materials;
interaction of radiation with matter; integrated optics, optoelectronics,
electro-optics, and magneto-optics; optical communications, modulation, computing,
and switching; ultrafast phenomena; far and near field models; IR, x-ray, and XUV optics;
application of optics to other scientific fields; atmospheric optics; lithography;
information processing and holography, correlators, pattern recognition,
and application of holography; detectors, sensors, and sources; imaging;
lasers and sources, laser materials and systems; vision.