The use of the quarter-wave optical thickness concept in the design of certain types of multilayer optical filters, or in the thickness determination of optical thickness of monolayers from transmission or reflection data, can present appreciable errors if dispersion is present in the layer optical constants. Moderate amounts of dispersion can cause significant shifts in the location of the global reflection or transmission extrema from what would be predicted using simple optical thickness considerations. Examples, including the use of measured index of refraction values for CeO2, are presented.
James W. Seeser, "Effect of Dispersion on the Reflection and Transmission Extrema from a Monolayer," Appl. Opt. 14, 640-642 (1975)