title: Evanescent modes in out-of-plane band structure for two-dimensional photonic crystals.
abstract: Reflection, diffraction and transmission of optical waves at the interface between a photonic crystal and the surrounding air can be described by propagating and evanescent Bloch modes. We have found such modes for one of the canonical two-dimensional photonic crystals, identical circular cylinders in a square pattern. We present computed out-of-plane band diagrams for propagating as well as evanescent modes, obtained with a numerical method based on Fourier-Bessel expansions. For a given frequency, all the modes are evanescent, except for a few low-order propagating modes. We find that most of the evanescent modes have a purely imaginary z-component of the Bloch wave vector, but many of the modes have a complex z-component.
authors.affiliation: University Graduate Center (UNIK), Kjeller, Norway. jakob.blad@unik.no
authors.forename: Jakob
authors.initials: J
authors.lastname: Blad
authors.forename: Aasmund S
authors.initials: AS
authors.lastname: Sudbø
mesh_terms: D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D008027:Light; D008420:Manufactured Materials; D008962:Models, Theoretical; D012031:Refractometry / Q000379:methods*; D012542:Scattering, Radiation