Antireflection coatings for two-dimensional photonic crystals using a rigorous impedance definition

We show that no consistent scalar definition of impedance is generally possible for photonic crystals. Instead, we present a rigorous semianalytic matrix definition of impedance for square lattice photonic crystals, defined in terms of Bloch modes. We then apply our definition to design a range of multilayer photonic crystal antireflection coatings efficiently. (C) 2008 American Institute of Physics.