Notch Filters

Notch filters, or stop-band filters, block a specific narrow wavelength range (stop band) and transmit broad wavelength ranges outside of this band. They feature high optical density, specified for the center wavelength of the stop band at 0° angle of incidence; as the angle of incidence increases, the stop band shifts to shorter wavelengths. Typical versions are UV fused silica filters for laser lines such as 488, 514, 532 and 561 nm, with the back side anti-reflection coated at the pass band regions.