Notch Filters or ‘Minus Filters’ are used to remove selected unwanted wavelengths, such as laser lines, by reflection. High transmission values in the adjacent passbands and steep transition edges are often necessary to maximise the required wavelengths.
Notch widths can be produced to suit the application requirements. Steep transition edges with low ripple and high %T utilise sophisticated designs with many layers. Such filters are available for the 300-8000nm region in a large variety of formats.