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Optical Coating

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An optical coating may be a simple layer of metal such as aluminum, or it may be a complex dielectric coating formed of multiple thin layers of material, where the composition, thickness, and number of layers is carefully controlled for a precise result.

Shanghai Optics is able to provide all types of anti-reflective, high reflective, and partial reflective coatings. Whether you need a single layer anti-reflective coating or complex multilayer dielectric stacks, we can manufacture exactly what you need. Dielectric coatings such as BBAR, V-coatings, dual wavelength coatings, and sharp cut-on and cut-off filters are available in stock.

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, or plasma assisted reactive magnetron sputtering, provides a good middle ground with reasonable quality and reasonable performance.

Examples of Optical Coatings

An anti reflective coating reduces unwanted reflection. For instance, a standard uncoated glass component will reflect about 4% of incident light. The same glass component with an AR coating tailored for the wavelength of light being transmitted might reflect less than 0.1% of incident light. We offer a variety of different dielectric anti reflective coatings, including both broadband and narrow band options. One versatile and hardwearing option is magnesium fluoride, which comes in both single-film and multiple layer options.

A reflective coating causes the surface to which it is applied to reflect all or some of the light which hits it. Consider again the uncoated glass optic with 4% reflection. Metal coatings will entirely change the properties of the optic. An aluminum coating will cause the same optic to reflect 88-92% of visible light. Silver coatings reflect 95-99% into the far infrared regions (reflection will be lower in the UV and some parts of the visible spectrum), and an appropriately chosen dielectric coating could increase reflectivity to 99.9%. Dielectric mirror coatings are often formed of two discrete repeating layers, one with a high index (for instance, ZnS or TiO2), and one with a low index (think MgF or SiO2). These high reflective dielectric coatings feature ultra high reflectance over a highly specific wavelength range, called the band stop.

A polarizing coating can be formed of a very thin film of a birefringent material, or alternately by means of interference effects in a multi-layer dielectric coating. If desired, polarizers can be designed to work with an incidence angle of 45 degrees, leading to a beam reflected at a 90 degree angle. Under certain circumstances, a polarizing coating on a lens or optical window can be used to replace polarizing prisms in an optical assembly.

A transparent conductive coating is a special type of coating that combines high transmission of visible light and electrical conductivity. These coatings can be used to protect the aperture of a device from electromagnetic interference, or to provide electrodes through which light can pass. The resistivity of a transparent conductive coating is specified in ohms per square, and may be anywhere from 4-1,000 ohms per square depending on application. ITO (indium titanium oxide) and AZO (aluminum doped zinc oxide) are two conductive coating options.

 

To learn more, visit: https://www.shanghai-optics.com/design/optical-coating.

To watch our optical coating video, visit: Optical Coating at Shanghai Optics - YouTube.