title: Unlocked evanescent waves in periodic structures.
abstract: We predict the existence of evanescent modes with unlocked phases in two-dimensional (2D) dielectric periodic structures. Contrary to what is known for one-dimensional structures, where evanescent fields lock to the host modulation, we show that in 2D systems a new class of evanescent modes exists with an unlocked real part of the wave vector. Hence, beams constructed from such unlocked evanescent waves can exhibit spatial effects. A significant focalization of a beam propagating within the band gap of a flat photonic crystal slab is also shown. The predicted phenomenon is expected to be generic for spatially modulated materials.
authors.affiliation: Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Urgell 187, Barcelona 08036, Spain. muriel.botey@upc.edu
authors.forename: Muriel
authors.initials: M
authors.lastname: Botey
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Cheng
authors.forename: Vicent
authors.initials: V
authors.lastname: Romero-Garcia
authors.forename: Ruben
authors.initials: R
authors.lastname: Picó
authors.forename: Ramon
authors.initials: R
authors.lastname: Herrero
authors.forename: Victor
authors.initials: V
authors.lastname: Sánchez-Morcillo
authors.forename: Kestutis
authors.initials: K
authors.lastname: Staliunas