All You Need to Know About Dielectric Mirrors


It can be said that a mirror has an important role in our lives. It can help us to do our daily, simple activities, such as grooming. It can also help with complex things, such as assisting a dentist to clean a patient’s teeth. A mirror works by reflecting electromagnetic radiation or light. So, it allows us to manipulate and switch light, depending on certain uses. Same as lenses can focus, magnify, and unite a light beam, a mirror is also able to do these functions in various applications.

Mirrors are available in several types, one of them is a dielectric mirror. Have you ever heard or used this type of mirror? This article will tell all you need to know about dielectric mirrors.

What is A Dielectric Mirror?

One film thin coating is frequently not enough to reach high reflectivity or selections of particular wavelength. In these cases, stacks of several thin-film coatings are required in order to get the desired spectral characteristics. Usually, these stacks consist of alternating thin film coatings of low and high refractive index dielectrics. When organized in this way, the mirror is called dielectric mirrors, which are also known as Bragg mirrors.

Generally, a multilayer stack is created by using advanced deposition techniques, such as IAD or Ion-Assisted Deposition, electron beam deposition, plasma-based film deposition, or ion beam sputtering. From a perspective of design, it is already proven that there is way greater control over the reflectivity using this approach than single metallic coatings. The refractive index of low index layers and high index layers, the number of dielectric pairs, the thickness of thin-film coatings, and the angle of incidence can all be setup to reach either broadband or narrowband wavelength properties, depending on the applications.

Applications of Dielectric Mirrors

  • Dichroic Mirrors

Some applications need wavelength selectivity for more than 1 wavelength. For example, in projection systems, a mirror is required in order to mix colors to get RGB colors in the projected image. In these applications, a white light source is divided into 3 different colors channels by using a dichroic mirror, modulated by the suitable LCD panels, and combined by using a trichroic prism in order to realize color projection.

  • Hot Mirrors

Similar to dichroic mirrors, there are some applications that need wavelength choice between the visible and infrared spectrum. The most common hot mirror application involves the reflection of infrared radiation from optical paths in order to minimize the effects of heat. The formation of heat cannot be avoided when using broadband light sources that emit wavelengths from the visible all the way up to the infrared.

Hot mirrors are increasingly used in cameras in order to reflect infrared wavelengths and only pass visible light. So that it allows high contrast photography, especially in special cases that need long exposure time. Hot mirrors are available in various sizes and shapes, such as round or square.

That is all of the information related to dielectric mirrors that you might want to know.

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