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Temperature-invariant and other narrow-band IR filters containing PbTe, 4-20µm

J S Seeley, R Hunneman, A Whatley

SPIE Proceedings, 246, Pages 83-94 (1980)


PbTe is unique amongst coating materials because of its negative temperature coefficient of refractive index. In combination with a conventional II-VI material it can confer immunity to temperature variation from at least -23°C to +110°C for a narrowband filter. It also has an absolutely large refractive index so that filters are attainable with minimal degradation when tilted, and a minimum number of layers overall particularly towards 20µm. Excellent transmission can be obtained.

DOI: 10.1117/12.959359

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