Suppression of reflection peaks in passbands of multilayer dielectric filters

In multilayer dielectric mirrors with one or more high reflectance bands in the near-ir and visible regions, large anomalous reflection peaks usually appear in the passbands. Their origin is traced to layer thickness inequality caused by unequal dispersions of the high and low index materials, and the common practice of monitoring layer thicknesses at stop bands. A procedure is described which takes account of the variations in materials dispersion in different coating laboratories, suppresses the anomalous reflection peaks, and locates the high reflection bands at their required wavelengths, with a relatively simple monitoring procedure.