Dielectric mirror

A dielectric mirror is a special kind of a mirror.

Dielectric mirrors are substrates made of glass (or sometimes other material) on which one or more thin layers of dielectric material are deposited, to form an optical coating. By careful choice of the type and thickness of the dielectric layers, the range of wavelengths and amount of light reflected from the mirror can be specified. The best mirrors of this type can reflect >99.999% of the light (in a narrow range of wavelengths) which is incident on the mirror.

Dielectric mirrors are often used for scientific optical work, eg. in lasers. They are also used in modern mirrorshades.

The manufacturing techniques for dielectric mirrors are based on thin-film deposition methods. Common techniques are molecular beam epitaxy, ion beam deposition, chemical vapor deposition, physical vapor deposition, and sputtering.

Dielectric mirrors are principially somewhat similar to anti-reflective coatings and dichroic filters.