Electromagnetic Properties of Ultrathin Quadrifilar Spirals and Their Complementary Structures

Published

Importance of diffraction in determining the dispersion of designer surface plasmons

Euan Hendry, Alastair P. Hibbins, and J. Roy Sambles, Physical Review B, Vol. 78, article 235426 (2008). Copyright © 2008 by the American Physical Society.By employing a modified modal matching approach, we obtain explicit analytical expressions relating frequency to in-plane wave vector for the surface electromagnetic mode confined at the interface between vacuum and a perfect conductor patterned with a two-dimensional square array of square holes. Our complete analytical formalism takes into account both multiple order waveguide modes and diffracted evanescent waves, hence overcoming the a priori assumptions intrinsic to previous descriptions of the dispersion of these surface waves. We validate our derived dispersion relation through comparison with that recently recorded at microwave frequencies using prism coupling. Finally, we show that diffracted evanescent waves play an important role in determining the dispersion, so that the electric field associated with “designer” surface modes is much more weakly confined to the interface than the field associated with surface plasmons on real metal surfaces

Subwavelength lateral confinement of microwave surface waves

Copyright © 2011 American Institute of PhysicsExperimental verification of the “domino plasmon,” recently proposed by Cano et al. [Opt. Express 18(2), 754, (2 010)] is presented. Using microwaves, it is demonstrated that this mode propagates along a periodic chain of metallic cuboids (“dominos”) and the dispersion of the mode is determined with results being compared to the predictions of analytical and numerical models. This mode is found to be surprisingly insensitive to the lateral width of the chain, even on a subwavelength scale. Having such tight confinement, “domino plasmons” show consider able promise for one-dimensional subwavelength guiding and focusing of electromagnetic fields

Ultrathin Quadrifilar Spirals and Spiral Ensembles

We investigate the eigenmodes of both ultrathin quadrifilar spirals and ensembles made up of such spirals by comparing experimental near-field scans with numerical finite-element models. These modes can be understood in the picture of electric and magnetic localized spoof plasmons.EPSRC through the QUEST programme; “The Quest for Ultimate Electromagnetics using Spatial Transformations (QUEST).

Tuning the polarization state of enhanced transmission in gratings

types: ArticleCopyright © 2008 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 92 (2008) and may be found at http://dx.doi.org/10.1063/1.2924317The polarization characteristics of enhanced transmission of lamellar gratings with structural dimensions on the subwavelength scale were studied and experimental results were compared to numerical models. The ability to tune the polarization state of the transmitted beam by varying the grating's structural parameters is discussed. Gratings were fabricated and tested in the microwave spectral region, and the results were compared to theoretically modeled results. Enhanced transmission produced by cavity modes was experimentally verified for both s-polarized and p-polarized incident beams of light. Applications of these results to photonic devices in the visible, infrared, and microwave spectral regions are discussed

The resonant electromagnetic fields of an array of metallic slits acting as Fabry-Perot cavities

Copyright © 2006 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 99 (2006) and may be found at http://link.aip.org/link/?JAPIAU/99/124903/1Fabry-Perot cavities are perhaps the best known of the optical transmission resonators, with cavity field enhancement accomplished by two parallel and partially reflecting planes. Recently it has been shown that arrays of narrow slits cut into a metal substrate are similarly able to exhibit resonant transmission modes. An analysis of the field solutions and transmission properties of this resonant array is compared to the well-known etalon and dielectric slab geometries, revealing a most elegant illustration of the principles of Maxwell's electromagnetism. It is demonstrated that the matching of the propagating field to each slit-cavity mode is made possible through strong diffraction at each end. Furthermore, the interface between the slit cavities and semi-infinite space beyond acts as a high-impedance surface on resonance, reflecting the field with a positive reflection-amplitude coefficient. Metallic slit arrays have several advantages over conventional Fabry-Perot resonators with interesting application potential

Excitation of remarkably nondispersive surface plasmons on a nondiffracting, dual-pitch metal grating

Copyright © 2002 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 80 (2002) and may be found at http://link.aip.org/link/?APPLAB/80/2410/1A nondiffracting metallic lamellar grating formed from three equally spaced grooves per repeat period, with one being slightly shallower than the other two is examined at microwave frequencies. When filled with a slightly lossy dielectric, this structure supports a remarkably nondispersive surface plasmon polariton mode, which exhibits strong selective absorption of incident power. Measured reflectivities show excellent agreement with the results predicted by a rigorous coupled wave theory

Microwave surface-plasmon-like modes on thin metamaterials

Matthew J. Lockyear, Alastair P. Hibbins, and J. Roy Sambles, Physical Review Letters, Vol. 102, article 073901 (2009). Copyright © 2009 by the American Physical Society.It has recently been shown that the structured surface of a perfect conductor can support surface-plasmon-like modes [Pendry et al., Science 305, 847 (2004)]. Such structures have a thickness of at least the order of the wavelength. Here, using microwave wavelength radiation incident beyond the critical angle of a wax prism, we quantify the surface-plasmon-like dispersion for a metamaterial surface with a thickness very much smaller than the incident wavelength

Electromagnetic response of closely spaced metal meshes

Melita Clare Taylor, Alastair P. Hibbins, and J. Roy Sambles, Physical Review B, Vol. 86, article 035126 (2012). Copyright © 2012 by the American Physical SocietyThe electromagnetic transmittance of a double layer of identical square arrays of square holes (mesh) in a perfectly conducting sheet is analytically modeled using a modal matching technique. The structure supports families of standing-wave modes together with surface modes that, close to the onset of diffraction, interact with each other. For frequencies below the onset of diffraction, it is the strength of this interaction mediated by evanescent diffraction in the near fields that dictates the electromagnetic response, which is studied as a function of mesh separation and the lateral misalignment between the meshes

Coupling of near-grazing microwave photons to surface plasmon polaritons via a dielectric grating

Copyright © 2000 by the American Physical SocietyA dielectric grating on top of a planar metal substrate is shown to couple near-grazing microwave photons to surface plasmon polaritons (SPPs). It is shown that when the grating grooves are oriented such that they are parallel to the plane of incidence (φ=90°), coupling to SPPs with both s- and p-polarized photons is possible at three different energies. It is demonstrated that one mode is coupled via p-polarized radiation and the other two modes are both coupled via s-polarized radiation. A multilayer, multishape differential grating theory allows the identities of each of the modes to be confirmed by modeling the electromagnetic fields above the metal substrate. In addition, a comparison between the experimentally derived reflectivity scans and the theoretical model is made.Defence Evaluation and Research Agency (DERA), Farnboroug