Notch filters, otherwise known as band-rejection or band-stop filters, are a type of optical filter designed to selectively reject a wavelength band and transmit at both longer and shorter wavelengths. Notch filters are often used throughout the coating industry to create components for various technological and scientific applications such as raman spectroscopy, laser-based fluorescence instrumentation, protection from laser radiation, and more.

Notch Filters in the Coating Industry

Ion-assisted electron-beam deposition technologies are the most widely used in coating manufacturing. This method features numerous advantages, such as a high deposition rate and excellent stress quality. To create notch filters using this deposition technique, it’s important to consider layer thickness constraints. If the layer thicknesses are not too thick or too thin, it allows for more accurate control of the index of refraction and thickness. 

Notch Filter Applications

Notch filters are used across various applications that require the transmission of some wavelengths while others need to be reflected or blocked. For example, many types of spectroscopy use this type of filter to assess the rotational and vibrational characteristics of molecular and crystal structures. This is especially beneficial in assessing how molecular structures react in specific environments as well as identifying unknown substances, detecting drugs, and analyzing forensic evidence. 

A crucial factor in determining a filter’s strength is optical density. These measurements help in the growth of a microorganism culture, measuring biomass concentration, and other analytical processes within the life science industry.

Another application of notch filters is with optical communications systems. These systems use notch filters to block any distortion that happens in a light pathway. Notch filters are also used frequently for laser safety applications, including laser eye protection. Safety glasses are designed and coated to reject harmful laser wavelengths.

Most notch filters offer up to 85% peak transmission. Notch filter designs are available for deposition onto polymers, fiber ends, semiconductor materials, crystals, glass, and other temperature sensitive materials.

Notch Filter Coatings from Evaporated Coatings

Notch coatings are effective in transmitting some wavelengths while blocking others, making them suitable for a range of optical applications throughout various industries. At Evaporated Coatings, we manufacture notch filters with up to three rejection bands. Our design team can work with you to determine your specific requirements including incident medium, angle of incidence, optical density, steepness of cut on and cut off transitions, and transmission wavelength range. As experts in optical coatings, we can deliver a notch filter solution that meets the needs of your unique application.

To learn more about our capabilities, or to get started on your custom notch filter solution, contact the experts at Evaporated Coatings today.