Study on spectral shift of infrared multilayer thin film filters by using of equivalent index locus

Spectral shift of infrared multilayer thin film filters, which use lead telluride and zinc sulfide as thin film materials, when used under cryogenic circumstance, was investigated. As the index of lead telluride varies with the change of temperature, its influence on the performance of filter must be taken into consideration when there is a temperature difference between preparation and application circumstance. A shift model was established on the basis of interlayer compensating effect of multilayer thin films, value of wavelength shift was calculated using equal dividing method, and the calculated result is well coincident with the measured one.