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High Performance Blocking Filters for the Region 1µm to 20µm

J S Seeley, S D Smith

Applied Optics, Vol. 5, No. 1 (1966)


A set of filters based on the sequence of semiconductor edges is described which offers continuity of short-wave infrared blocking. The rejection throughout the stop region is greater than 10-3 for each filter and the transmission better than 70% through one octave with a square cut-off. The cut-off points are located at intervals of about two-thirds of an octave. Filters at 2.6µm, 5.5µm, and 12µm which use a low-passing multilayer in combination with a semiconductor absorption edge are described in detail. The design of multilayers for optimum performance is discussed by analogy with the synthesis of electric circuit filters.