Armstrong K R, Low F J
Appl Opt. 1974 Feb 1;13(2):425-30. doi: 10.1364/AO.13.000425.
High transmission, low pass scatter filters for blocking at wavelengths from 3.5 microm to 50 microm and singlelayer antireflection coatings for optical materials used in the 25-microm-300microm region of the spectrum are described. The application of both techniques to liquid-He-cooled filters permits the construction of efficient low pass and medium-width band pass filters for use throughout the far infrared.