Two types of multilayer interference filter are required for temperature sounding the earth’s atmosphere. In relation to the 668-cm-1 ν2 band of CO2 these are narrowband (4 cm-1 wide for the Q branch, 10 cm-1 for the R branch) or isolation (~60 cm-1 wide for the complete center of the band). Difficulty in manufacturing the filters for NIMBUS-SCR and -PMR spaceflight has indicated a need for improvement in the monitoring and control of the deposition of layers, and the paper describes a realization of this. The consequent effect on filter performance (utilizing a particular combination of layer materials) is described.
C. S. Evans, R. Hunneman, J. S. Seeley, and A. Whatley, "Filters for ν2 band of CO2: monitoring and control of layer deposition," Appl. Opt. 15, 2736-2745 (1976)