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Dichroic Filters


dichroic filtersKnight Optical can offer a range of dichroic filters as part of our catalogue. Our filters offer superior reflection and transmission spectral properties, whilst exhibiting minimal absorption.

Dichroic filters are manufactured by applying a thin-film layer to a substrate such as soda-lime glass or borosilicate, by controlling these layers the transitions can be sharper and more precise.

Below are the different types of dichroic filters Knight Optical have available as part of our catalogue products:

  • Our shortpass dichroic filters have a high transmission before the cut-off, and then a high reflection band after. Knight Optical currently offer shortpass dichroic mirrors with cut-off wavelengths ranging from 414nm to 730nm.
  • Knight Optical’s longpass dichroic filters have transmission and reflection bands divided by the cut-on wavelength, wavelengths before this cut-on point are reflected, whilst the longer wavelengths are transmitted. Knight Optical offer longpass dichroic filters with cut-on wavelengths from 420nm up to 740nm.
  • The bandpass dichroic filters will only transmit a certain waveband whilst blocking (in this case through reflection) the wavelengths either side. Knight Optical stock bandpass dichroic mirrors with passbands centred from 350nm to 850nm.
  • Colour correction filters offer pure, true to life colour temperature adjustment for entertainment and photography. Knight Optical has daylight and tungsten conversions available.


Where our stock products do not meet your requirements, Knight Optical excels in custom orders, providing optics that are manufactured to our customers specifications. We are able to provide custom dichroic filters for general and precision applications with spectral performance to suit your needs and budget. For a quick turnaround, Knight Optical have large 1.1mm thick coated sheet material which can be cut to your requirements, browse our stock coatings to see if these meet the spectral requirements. Fully customised options are also available with different



For further information on our dichroic filters or help with your enquiry, please contact our technical sales team directly or click the enquiry button below.

Knight Optical’s Dichroic vs. Interference Bandpass Filters

Both filter types are made by depositing thin-film layers of material (usually a metal or dielectric material) to a substrate, which selectively transmits certain wavelengths and reflect the unwanted wavelengths.

However, Knight Optical’s interference bandpass filters are designed to have much narrower bandwidth with steeper slopes and are generally manufactured using stacks of these substrates with controlled thin-layers of materials. This is why our interference filters are mounted.

Knight Optical has a vast catalogue of interference bandpass filters in 12.5mm, 25mm, and 50mm mounts with centre wavelengths (CWL) ranging from 214-2000nm.

Quality Assurance

All dichroic filters are tested in our metrology laboratory to ensure they pass their specifications. The transmission and reflection requirements are critical and these are checked with our Cary 7000 Spectrophotometer which can test these at differing angles of incidence.

Typical Applications

  • Dichroic filters, or dichroic mirrors, are often used in fluorescence microscopy and act as a beamsplitter to direct the excitation and emission beams towards the sample or detector. Knight Optical has a range of fluorescence filter sets including excitation and emission bandpass filters and a dichroic mirror, suitable for a variety of fluorophores.
  • They can be used as wavelength separators in laser systems (harmonic separators), here are a high damage threshold needs to be specified to ensure usability with the laser system.

Our 2022/2023 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
Click below to view our digital catalogue now.

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