Definition of dichroic coating

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Photonics Dictionary

dichroic coating: A dichroic coating, also known as a dichroic filter or dichroic mirror, is an optical coating designed to selectively transmit or reflect certain wavelengths of light while simultaneously absorbing or transmitting others. The term "dichroic" comes from the Greek words "di" meaning two, and "khroic" meaning color, indicating that these coatings exhibit different optical properties depending on the wavelength of light.

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Dichroic coatings achieve their selective transmission and reflection properties through interference effects created by thin-film layers deposited onto a substrate. These thin-film layers are precisely engineered to have thicknesses that interact with specific wavelengths of light, causing constructive interference for desired wavelengths and destructive interference for others. Key characteristics of dichroic coatings include:

Selective transmission and reflection: Dichroic coatings can transmit light of certain wavelengths while reflecting others. This property allows them to separate or combine light of different colors or wavelengths, making them useful in various optical applications.

High efficiency: Dichroic coatings are designed to have high transmission or reflection efficiency for targeted wavelengths, minimizing energy loss and maximizing the desired optical effect.

Wide range of applications: Dichroic coatings are used in numerous applications, including optical filters, mirrors, beam splitters, color separation in lighting fixtures, and optical components for spectroscopy and microscopy.

Customizable properties: The optical properties of dichroic coatings, such as the wavelengths of transmission and reflection, can be tailored by adjusting the composition and thickness of the thin-film layers during the deposition process.

Durability: Dichroic coatings are typically deposited using techniques such as physical vapor deposition (PVD) or ion beam sputtering, resulting in durable and long-lasting optical coatings resistant to environmental factors such as moisture and abrasion.