An optical coating is a thin-film deposit used to enhance transmission, change reflective properties, or change the polarization of light transmitted through an optical component.
Shanghai Optics can provide all types of anti-reflective, high reflective, and partial reflective coatings. We produce a wide variety of coatings from a single layer of anti-reflective coating to complex multilayer dielectric stacks. Types of dielectric coatings are BBAR, V-coatings, dual wavelength coatings, and sharp cut-on and cut-off filters.
At Shanghai Optics we use a variety of different methods to produce high quality optical coatings. These methods include plasma sputtering, ion beam sputtering, atomic layer deposition, and evaporative deposition.
Ion beam sputtering and atomic layer deposition provide the highest spectral performance, high durability and high repeatability; but the manufacturing process is slow and expensive. Evaporative deposition is more budget friendly, and plasma sputtering provides a good middle ground with reasonable quality and reasonable performance.
In ion beam sputtering (IBS) we use a high energy electric field to accelerate a beam of ions, giving them kinetic energy of 10-100 eV. The ion beam hits the source material, and ions from this material sputter onto the optical surface. A dense film is formed upon contact. Since every step of this process is carefully monitored and precisely controlled, the result is a highly consistent coating that meets design specifications and parameters precisely. IBS coatings can even have less roughness than the original substrate does. This is the method used to make “super mirrors”, special coated mirrors with a reflectivity of more than 99.99%.
In atomic layer deposition the optic to be coated is placed in a vacuum chamber, often at elevated temperatures. The coating substance is delivered as a gas, in pulses. During each pulse a single layer adheres, and then the vacuum chamber is evacuated in preparation for the next pulse. The benefit of this method is an extremely high level of control in layer thickness and composition of the layers of material, and the ability to uniformly coat optics with any geometry. The only negative side to this method is that it is slow, and hence expensive to run.
The final properties of a dielectric coating will depend on the coating materials used in the thin film layers—especially their refractive index. Changing the layer thickness and the number of layers can also completely change the function of a thin film coating. The ideal optical coating designs for your application will depend on your wavelength range and work environment as well as on your project budget. Our design team has many years of experience and we would be happy to help you determine the custom optical coatings that best fit your application.