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

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

Transmission of microwave radiation through a sub-wavelength slit with internal structure

Copyright © 2008 Society of Photo-Optical Instrumentation Engineers. This paper was published in Proceedings of SPIE Volume 6987, article 69871V and is made available with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Fabry-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. Here, the transmission of normally incident plane wave microwaves through a single stepped sub-wavelength slit in a thick metal plate is explored. The presence of the step substantially increases the radiation wavelength, which may be resonantly transmitted to well beyond twice the plate thickness. Insight into the resonant behaviour of the stepped slit is provided through the analysis of the field solutions produced by a finite element model. This model also predicts resonant transmission which is in excellent agreement with the experimental results

Transmission of microwaves through a stepped subwavelength slit

Copyright © 2007 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 91 (2007) and may be found at http://link.aip.org/link/?APPLAB/91/251106/1The transmission of normally incident plane wave microwaves through a single stepped subwavelength slit in a thick metal plate is explored. The presence of the step substantially increases the radiation wavelength which may be resonantly transmitted to well beyond twice the plate thickness. Insight into the resonant behavior is provided through analysis of field solutions produced by a finite element model

Surface plasmons on metamaterials

Copyright © 2008 Society of Photo-Optical Instrumentation Engineers. This paper was published in Proceedings of SPIE Volume 6987, article 698712 and is made available with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.The field of plasmonics has historically been a playground exclusively for the optics community. Primarily this is because the response of metals becomes dominated by their large conductivities at much lower frequencies, making it difficult to exploit the unique properties of surface plasmon (SP) modes. Indeed SPs on flat, perfectly conducting substrates are better described as simple surface currents or grazing photons. However the realization that one can form metal-dielectric composites to support surface waves with plasmon-like properties has opened the field of plasmonics to the terahertz and microwave domains. Pendry et al. [Science, 305, 847 (2004)] were among the first to speculate about an extension of plasmonics into long wavelength regimes. They demonstrated that the perforated surface of a perfect conductor can support a SP-like mode whose behavior is determined purely by the geometry of the substrate. Beginning with our initial experimental verification of these SP-like modes excited via grating-coupling, we present an overview of some of our recent microwave studies. We progress to study the classical method of prism coupling and also consider the enhanced transmission phenomenon (mediated by plasmon-like surface modes) through hole arrays. Finally the first experimental evidence of coupled SP-like modes between two such perforated metal substrates placed in close proximity will be presented

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

Low angular-dispersion microwave absorption of a dual-pitch nondiffracting metal bigrating

Copyright © 2003 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 83 (2003) and may be found at http://link.aip.org/link/?APPLAB/83/806/1The surface plasmon modes supported by a nondiffracting 90° bigrating consisting of three grooves per repeat period with one slightly shallower than the other two are characterized by studying the reflectivity from the structure as a function of the angle of incidence and the incident wavelength (11.3<λ0<16.7 mm). This structure supports two remarkably angle-independent modes plus a further, lower-energy mode which is more dispersive. Experimental reflectivity is compared with that calculated using a finite element model. In addition, to understand the character of each of the modes, the spatial form of the electromagnetic fields at the resonant frequencies are explored

Resonant transmission of light through finite chains of subwavelength holes

In this paper we show that the extraordinary optical transmission phenomenon found before in 2D hole arrays is already present in a linear chain of subwavelength holes, which can be considered as the basic geometrical unit showing this property. In order to study this problem we have developed a new theoretical framework, able to analyze the optical properties of finite collections of subwavelength apertures and/or dimples (of any shape and placed in arbitrary positions) drilled in a metallic film.Comment: Accepted for publication in Phys. Rev. Let

Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?

The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area

Ultrafast optical switching of the THz transmission through metallic subwavelength hole arrays

Euan Hendry, Matthew J. Lockyear, J. Gómez Rivas, L. Kuipers, and M. Bonn, Physical Review B, Vol. 75, article 235305 (2007). "Copyright © 2007 by the American Physical Society."We demonstrate ultrafast optical switching of the transmission of terahertz radiation through a metal grating with subwavelength holes. By fabricating the grating on a semiconductor silicon substrate, we are able to control the grating transmission intensity by varying the photodoping level of the silicon and thereby the resonant coupling to the metal grating. As such, we are able to switch the transmission on picosecond time scales with low visible light intensities, observing a factor of 2–5 improvement in photomodulation efficiency at resonance wavelengths over a bare silicon surface