On the Limiting Band Width of Interference Filters

Abstract

The effects of variations of the thickness of the individual layers of an interference filter made with dielectric multilayers are examined, with respect both to the displacement of the pass band and to its width as affected by random fluctuations in these thicknesses. It is shown that the use of special multilayer stacks having a large dispersion of the phase change on reflection can yield a much greater resolution only in the case of perfectly uniform films. The insensitivity of the pass band to variations of the spacer layer is compensated by a correspondingly large sensitivity to variations of the layers constituting the `mirrors'. It is also shown that the effect of random thickness variations is a minimum when the sensitivities of all layers are proportional to their thicknesses. Sample calculations and experimental illustrations are given.