What are thin-film optical filters?

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What are thin-film optical filters?
Thin-film optical filters are made by depositing alternating thin layers of materials with special optical properties onto a substrate, such as optical-grade glass. As light makes its way through the optical filter, its direction changes as it passes from one layer to the next, resulting in internal interference. This is due to the differences between the refractive indices of the materials in the dielectric thin-film coating. The configuration of the layers results in an optical filter that manipulates different wavelengths of light in different ways. Depending on the wavelength and type of optical filter, light can be reflected off of the filter, transmitted through it, or absorbed by it.

Optical filters can be designed to transmit, block, or reflect light at any wavelength range from the UV to the IR. They are generally classified into five basic categories based on their spectral shape.
Bandpass, notch, and edge filters are generally designed to work at 0° or other small angles of incidence (AOI). Dichroic filters, on the other hand, are meant to be used at 45° or other large AOI and can be designed in bandpass, notch, or edge configurations.

Optical filters can also be designed in multiband configurations. Multiband filters are bandpass filters with more than one passband, or region of high transmission. Multi-notch filters have more than one blocking region and transmit all adjacent light. Polychroic filters are dichroic filters that have multiple bands or notches.

Although most optical filters fall into the above categories, custom filters can be designed with any spectral shape imaginable. For example, when transmitted through a specifically designed custom filter, light from a xenon lamp can be transformed to mimic the spectrum of the sun. Other custom filters are designed to match arbitrary spectral shapes.

Because of their versatility, optical filters are used in a multitude of applications. Fluorescence microscopy, astronomy, solar imaging, remote sensing, Raman spectroscopy, and telecommunications are just a few disciplines that rely on optical filters as a key component of their systems.

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Advanced plasma deposition. Precision wavelength control. New metrology techniques. Learn how our thin-film coating technology has enabled the routine production of optical components with performance and prices that were previously impossible.  learn more...

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Our technology enables the routine production of optical filters with performance and price characteristics that were previously impossible. These informative white papers help our customers and partners maximize the advantage they gain by using our filters.

Thin film optical coatings. Setting the new standard.
Alluxa is an ISO 9001:2008 certified, ITAR registered, highest performance optical filter and optical coating manufacturer located in Santa Rosa, CA. Founded in 2007 by a team of thin-film deposition veterans; Alluxa's core team brings together decades of expertise and diverse backgrounds in deposition, automation, metrology, and optics.

Alluxa produces its filters with a new class of custom optical thin-film coating equipment designed and built by our team. The combination of our state-of-the-art automation, proprietary control algorithms, and our SIRRUS plasma deposition process allows the world's most difficult filters to be created in a fraction of the time required by other hard coating methods. Our proprietary thin-film optical coating platform allows us to reliably and repeatedly reproduce the same high-performance optical thin films over several different coating runs which translates to consistent performance across all of your systems.

Alluxa is delivering custom solutions to the most challenging optical coating problems at competitive pricing. Learn more about our custom and OEM filter offeringsrequest a quote, or shop our catalog of in-stock and available optical filters.