title: Diffraction and localization in low-dimensional photonic bandgaps.
abstract: We show that, in low-dimensional photonic bandgaps, wave diffraction resulting from localization in the translational-invariant directions is strongly influenced by the photonic band structure of the periodic crystal, leading to new kinds of wave localization. In particular, for a periodic layered structure we show that, close to a bandgap edge, diffraction is enhanced, with a transition from a parabolic diffraction curve-typical of isotropic media and supporting Gaussian beams-to hyperbolic or elliptic diffraction curves. In the last two cases localization in the form of stationary X-shaped or sinc-shaped waves is possible.
authors.affiliation: Dipartimento di Fisica and Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Richerche, Politecnico di Milano, Piazza L. da Vinci, 32 I-20133 Milano, Italy. longhi@fisi.polimi.it
authors.forename: Stefano
authors.initials: S
authors.lastname: Longhi
authors.forename: Davide
authors.initials: D
authors.lastname: Janner