One-dimensional photonic crystals of inhomogeneous thin films: band structure of rugate filters

The properties of one-dimensional photonic crystals of inhomogeneous thin films whose refractive index function is periodic are analyzed by using the formalism of equivalent layers. With this method it is possible to consider the so called rugate filters as single thin films with equivalent optical admittance and equivalent phase thickness functions, that provide information about their band structure, and conditions of existence of surface modes that appear when a finite rugate is in contact with any bulk media or other photonic crystal.