A Fabry-Perot interferometer having quartz plates coated with 9-layer dielectric films is used to study the dispersion of the phase change that occurs on reflection from such films. Using the secondary wavelength standards from the iron arc, it is shown that the method of exact fractions may be employed to establish the correct numbering of orders, but that it must be combined with a theoretical calculation of the phase change. The dispersion of phase change for the recently developed broad-band multilayers is found both theoretically and experimentally (by the use of Fizeau fringes) to be as much as 17 times as great as for the conventional multilayers. This fact gives unique properties to an interference filter incorporating two such multilayer films. Chief among these is the existence of several very narrow pass-bands, and an insensitivity to variations of the spacer thickness.
P. W. BAUMEEISTER and F. A. JENKINS, "Dispersion of the Phase Change for Dielectric Multilayers. Application to the Interference Filter," J. Opt. Soc. Am. 47, 57-59 (1957)