Optical Coating

Optical coatings are used primarily to coat optical devices, such as lenses and mirrors, to alter the way light interacts with the device. Because optical devices depend on either the proper transmission or reflection of light, the presence of an optical coating enables the device to function properly and achieve the level of transmission or reflection

needed. The process by which an optical device is made more reflective is called silvering—highly reflective metals, such as aluminum and silver, are often used in optical coatings to silver an optical device. Optical devices that require minimized reflectivity, on the other hand, tend to benefit more from antireflection coatings. Product Variants: Types of Optical Coatings

Depending on the desired result—either increased or decreased reflectivity—various optical coatings can be applied to create or enhance a device’s properties.

Key Terms

There are several key terms that may help during optical coating selection: dielectric, refractive index, reflective, antireflective broadband, wavelength and visible spectrum.

Dielectric

A dielectric material is an insulator, meaning it is not a good conductor of electric current. However, dielectric materials can support electrostatic fields, with makes them relatively versatile materials.

Refractive Index

A refractive index, also called an index of refraction, is a measure of a material’s ability to slow down light waves as they pass through. A material’s index of refraction is determined by the ratio of the speed of light in a vacuum to the speed of light in the material.

Reflective

A reflective material does not transmit light waves, but rather bounces light waves back. A mirror is an example of a highly reflective material.

Antireflective

An antireflective material is the opposite of a reflective material. Instead of reflecting light waves, an antireflective material reduces reflection, which can, in some cases, improve contrast.

Broadband

The term broadband refers to having a wide band (and a continuous spectrum) of electromagnetic frequencies. Sunlight is an example of a type of broadband light radiation.

Wavelength

A wavelength is the distance between one peak of a wave and the next; in this context, between one peak of a wave of light and the next.

Visible Spectrum

The visible spectrum refers to the range of wavelengths of visible light radiations, as can be seen in the distribution of colors created when light is dispersed by a prism.