Graphical displays of complex reflectance for nonabsorbing multilayer optical coatings based upon circle diagrams are presented. Similar displays are then developed for absorbing films. The two types of display are used to analyze several common multilayers, and a repetitive structure with period characteristics is introduced.
Joseph H. Apfel, "Graphics in Optical Coating Design," Appl. Opt. 11, 1303-1312 (1972)