Mirror coatings work in the opposite way of an anti-reflective coating. Instead of reducing the amount of light reflected, its job is to reflect as much light as possible at a given wavelength or over a particular wavelength range. Compared to a household mirror, optical mirrors are precision substrates with thin layer depositions of metallic and/or dielectric materials.
Typical metallic coatings are silver, gold, or aluminum. A protective layer of silicon dioxide (SiO2) is often deposited on top of a metallic coating to increase the durability. Sometimes dielectric materials are deposited below the metal coating to help provide spectral enhancement.
For particular applications, Precision Optician’s bevy of advanced coating equipment allows us to deposit multilayer dielectric mirrors for even higher spectral performance at custom wavelengths or wavelength ranges. In addition, Precision Optical has the ability to deposit dichroic mirror coatings, which offer very high reflectance in one band, with very low reflectance in another. These coatings are dubbed ‘hot’ or ‘cold’ mirrors.