High performance multilayer interference filters for the region 12-50µm
C S Evans, R Hunneman, J S Seeley
Journal of Physics D, Vol 9, Pages 309-320 (1976)
The realization of filters containing PbTe and various II-VI materials to an optimum performance is described. In the pass-band, transmission is optimum due to the use of the Tschebysheff equal-ripple design concept; in the stopping bands, performance is optimum due to PbTe photoconductive absorption (low-pass) and II-VI reststrahl absorption (high-pass). Two example filters are discussed in detail: a cut-on/cut-off filter for the 668 cm-1 v2 band of CO2 useful in space research, and a long-wave blocking filter cutting on at 490cm-1 useful in infrared grating spectrophotometers.