The coupling of microwave radiation to surface plasmon polaritons and guided modes via dielectric gratings

Copyright © 2000 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 87 (2000) and may be found at http://link.aip.org/link/?JAPIAU/87/2677/1It is shown that an absorbing dielectric layer, sinusoidally modulated in height, on top of a planar metal substrate, may be used to provide coupling between both s- and p-polarized incident microwave photons and surface plasmon polaritons, which propagate along the metal–dielectric interface. The study is carried out using paraffin wax as the dielectric material on an aluminum-alloy plate and the wax is sufficiently thick such that it may also support a guided mode. Energy reradiated from these excited modes into diffracted orders is recorded by monitoring the specular beam reflectivity as a function of wavelength (7.5<λ0<11.3 mm) and azimuthal angle of incidence (0°<φ<90°). The azimuthal-angle-dependent reflectivity scans are fitted using a multilayer, multishape differential formalism to model conical diffraction with a single set of parameters describing the grating profile, and the permittivity and thickness of the wax layer

Resonantly induced transparency for metals with low angular dependence (article)

This is the final version of the article. Available from AIP Publishing via the DOI in this record.The dataset associated with this article is in ORE: http://hdl.handle.net/10871/24757Thin (sub skin-depth) metal layers are known to almost completely reflect radiation at microwave frequencies. It has previously been shown that this can be overcome at resonance via the addition of closely spaced periodic structures on either side of the film. In this work, we have extended the original one-dimensional impedance mechanism to the use of two-dimensional periodic structures both experimentally and analytically using an equivalent circuit approach. The resulting device shows experimentally a low (<5% relative frequency shift) dependence in both angle of incidence and polarisation. We also show that the same principle can be used to transmit through a thicker (∼μm) perfectly conducting film perforated with a non-diffracting (short pitch) array of subwavelength holes with the cut-off frequency above 900 GHz showing resonant transmissivities in the 20–30 GHz range above 40%.The authors wish to acknowledge the financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom, via the EPSRC Centre for Doctoral Training in Metamaterials (Grant No. EP/L015331/1). All data created during this research are openly available from the University of Exeter's institutional repository at https://ore.exeter.ac.uk

Spatial transformations: from fundamentals to applications

We acknowledge the financial support of the Engineering and Physical Sciences Research Council (EPSRC), via the programme grant ‘The Quest for Ultimate Electromagnetics using Spatial Transformations (QUEST)’, grant no. EP/I034548/1

A broadband stripline technique for characterizing relative permittivity and permeability (article)

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.The dataset associated with this article is located in ORE at: https://doi.org/10.24378/exe.503We present a stripline design and calibration method allowing the extraction of relative permittivity of single dielectric samples in the 200 MHz – 50 GHz range. The simultaneous extraction of relative permittivity and permeability is also illustrated by characterizing a set of samples comprising magnetic inclusions over the same frequency range. The calibration method involves the use of seven measurements of the stripline scattering parameters (S-parameters) with different length shorts inserted. From these measurements, it is possible to determine the reflections at the transition regions of the stripline to correct the measured S-parameters for characterization. By quantifying a range of samples with increasing percentage volume filling of barium titanate in polyurethane for the case of dielectric samples, and carbonyl iron powder (CIP) for magnetic samples, this work demonstrates a reliable method for the broadband characterization of composite materials.This work was supported by The Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom and The Defence Science and Technology Laboratory (DSTL) of The United Kingdom, via the EPSRC Center for Doctoral Training in Metamaterials (Grant No. EP/L015331/1

Microwave superdirectivity with dimers of helical elements

This is the final version. Available from the American Physical Society via the DOI in this recordSuperdirective end-fire radiation in the low GHz frequency range is demonstrated using magnetically-coupled structures of subwavelength metallic helices. Numerical, experimental and analytical results are presented on superdirective dimers that are almost three times smaller compared to previously demonstrated dimers of split-ring-resonators (0.09λ compared with 0.25λ) and provide close to theoretical maximum values of directivity without using complex feeding networks. The size, directivity, efficiency and operational passband width of such structures is optimized.Engineering and Physical Sciences Research Council (EPSRC

A ferrite-filled cavity resonator for electronic article surveillance on metallic packaging (article)

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThe dataset associated with this article is located in ORE at: https://doi.org/10.24378/exe.1924Conventional electronic article surveillance (EAS) tags are ineffective on metallic packaging. The component of RF magnetic field perpendicular to the surface of the packaging induces eddy currents that suppress the magnetic flux linking the inductive element of the tag. In this work an inductive quarter-wavelength planar cavity, formed by wrapping aluminum foil around a ferrite core, was extended by wrapping additional capacitive layers of foil/dielectric around the ferrite-filled central region. This so-called ‘wrapped tag’ exhibits the frequency, Q-factor, and read distance characteristics of existing EAS tags, but is instead driven by RF magnetic fields parallel to the surface of the metallic packaging. In this article we compare the observed frequency response of the wrapped tag with a simple LC-resonator model that takes account of the tag’s geometrical features, and use the model to describe how the design and construction of the tag can be optimized. Finite element method modeling is used to reveal how the current flows in the wrapped foil of the tag. Prototype tags show good reproducibility, demonstrating the potential of the design as a solution to the problem of tagging metallic packaging in the EAS industry.Engineering and Physical Sciences Research Council (EPSRC)QinetiQ Ltd

Selective transmission through very deep zero-order metallic gratings at microwave frequencies

Copyright © 2000 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 77 (2000) and may be found at http://link.aip.org/link/?APPLAB/77/2789/1Zero-order metal grating structures are found to give extraordinary selective transmission at microwave frequencies through the resonant excitation of coupled surface waves. The metal slat structures with dielectric spacings as small as 250 µm strongly transmit wavelengths of several millimeters. A simple interpretation of these novel results which treats the deep grating structures as "filled" Fabry–Perot cavity systems gives model transmissivities which agree very well with the experimental data