title: Closure of the stop-band in photonic wire Bragg gratings.
abstract: Photonic Wire Bragg Gratings, made by periodic insertion of lateral rectangular recesses into photonic wires in silicon-on-insulator, can provide large reflectivity with short device lengths because of their large index contrast. This type of design shows a counter-intuitive behaviour, as we demonstrate - using experimental and numerical data - that it can have low or null reflectance, even for large indentation values. We provide physical insight into this phenomenon by developing a model based on Bloch mode theory, and are able to find an analytical expression for the frequency at which the grating does not sustain the stop-band. Finally we demonstrate that the stop-band closing effect is a general phenomenon that may occur in various types of periodic device that can be modeled as transmission line structures.
authors.affiliation: Dipartimento di Elettronica, Informatica e Sistemistica, University of Bologna, Viale Risorgimento 2, I 40136 Bologna, Italy. marco.gnan@unibo.it
authors.forename: M
authors.initials: M
authors.lastname: Gnan
authors.forename: W C L
authors.initials: WC
authors.lastname: Hopman
authors.forename: G
authors.initials: G
authors.lastname: Bellanca
authors.forename: R M
authors.initials: RM
authors.lastname: de Ridder
authors.forename: R M
authors.initials: RM
authors.lastname: De La Rue
authors.forename: P
authors.initials: P
authors.lastname: Bassi
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers