Optical Notch Filters also known as Optical Band Stop Filters or Optical Band Reject Filters are optical components designed to block specific wavelengths of light in selection while allowing others to pass through with little hindrance. Notch filter offers high transmission out of the stop band and large attenuation to the wavelengths outside the stop, enabling isolation of spectral regions or suppressing unwanted background noise. In fact, an optical notch filter can be viewed as an inverse of a bandpass filter.

Several important key parameters need to be taken into consideration when selecting notch filters specified to your requirements: stop band wavelength (i.e., the wavelength range at which the light signal will be blocked), power handling capabilities (i.e., the maximum power threshold tolerable for the filter), and the most important factor, optical density, which determines the rejection strength of an optical notch filter. To be more precise, the formulated relationship between OD and Transmission% is OD=log10 1/T where OD is optical density and T is absolute transmittance. 

With sharp transition slopes at the rejection and transmission regions, our optical notch filters deliver optimized results in various optical applications where spectral control is paramount. For instance, in spectroscopes, notch filters are used to remove unwanted spectral lines or laser wavelengths, allowing researchers to focus on the target signals of interest. Besides, notched filters are also utilized in fluorescence microscopes and biochemical lasers, allowing for the investigation of molecular interactions and the identification of chemical compounds. The notch filters we supplied in North Optics cater to an extensive spectrum, with their standard or custom center wavelengths covering the common laser line wavelengths of 405nm, 488nm, 514nm, 533nm, 561nm, 594nm, 633nm, 658nm, 785nm, 808nm, 980nm, and 1064 nm, and other UV, VIS, IR wavelengths.

This page specifies North Optics's Off-the-shelf Optical Notch Filters. Our optical band stop filters consist of  BK7 or UV Fused Silica substrate stacked with dielectric coatings, which attenuate the light within the rejection band through destructive interference and reflection, the available standard optical densities can be <OD3 or OD4, while the out-of-band transmission is >90% or can be customized. All the optical notch filters are mounted in black anodized Aluminum rings for ease of handling, the ring can further increase the optical density by ameliorating scattering. Custom notch filters with a maximum rejection depth of OD6 and other selectable specifications are also available.

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