Beruete, M.

Navarro-Cia, Miguel

Orazbayev, B.

Pacheco-Peña, V.

English

Lenses, as optical instruments, have been known for centuries. With theappearance of Kock’s metallic lenses, and later metamaterials, which allowtailoring both permittivity and permeability, the lenses have gained a renewedlook. This great deal of effort has paid off resulting in perfect lenses, superlenses, hyperbolic lenses, chiral lenses, transformation optics lenses, epsilon-near-zero lenses, etc. One of the promising practical realizations of a metamaterial lens is the fishnet metamaterial lens. Consisting of stacked subwavelength hole arrays and working in the realm of the extraordinary transmission, the fishnet metamaterial offers lower losses and frequency-robust magnetic response. Although showing a good performance, plano- and bi-concave fishnet lenses are relatively voluminous. This problem can be solved by applying the well-known zoning technique, whereby the redundant material is removed when one wavelength phase shift in it is reached. Such a technique was successfully applied in the previous works and demonstrated the reduction of the weight and absorption losses, but for single-frequency operation (V. Pacheco-Peña et al., Appl. Phys. Lett., 103, 183507, 2013; V. Pacheco-Peña et al., J. Appl. Phys., 115, 124902, 2014).The operational band can be broadened by applying an improved zoning technique, which exploits a strong dispersion of the fishnet. A best fittingprocedure, which minimizes the root-mean-square-error between the smoothanalytical profile and its staircase approximation (defined by the fishnet unit cell)for the whole band, is applied to the conventional zoning technique. As a result,the optimal zoned lens profile is obtained. It should be noticed that the resultingprofile is completely different from that used in previous works, where it wasobtained only for a single frequency.In this communication, we present a broadband zoned fishnet lens designed byusing the smart optimization procedure described above. The lens was abricatedand its performance was investigated experimentally at frequencies f1 = 54 GHzand f2 = 55.5 GHz. The results were compared against analytical calculationsbased on the Huygens-Fresnel principle, and full-wave numerical simulations.The results demonstrate a good agreement with the design parameters and anenhancement above 9 dB in the frequency range 54-58 GHz, while the zoned lens optimized for single-band operation achieves enhancement values above 9 dB only at the design frequency range, 55 - 56.5 GHz. The numerical andexperimental results of a proposed lens antenna show directivities above 15 dBfor both frequency bands

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  University of BirminghamA broadband fishnet metamaterial lensOrazbayev, B.; Pacheco-Peña, V.; Beruete, M.; Navarro-Cia, MiguelDocument VersionPeer reviewed versionCitation for published version (Harvard):Orazbayev, B, Pacheco-Peña, V, Beruete, M & Navarro-Cia, M 2015, A broadband fishnet metamaterial lens. inIEEE AP-S International Symposium on Antennas and Propagation 2015 and USNC/URSI National RadioScience Meeting 2015 (2015 IEEE AP-S/URSI), Vancouver, Canada, July (2015). pp. 1.Link to publication on Research at Birmingham portalGeneral rightsUnless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or thecopyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposespermitted by law.•	Users may freely distribute the URL that is used to identify this publication.•	Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of privatestudy or non-commercial research.•	User may use extracts from the document in line with the concept of ‘fair dealing’ under the Copyright, Designs and Patents Act 1988 (?)•	Users may not further distribute the material nor use it for the purposes of commercial gain.Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document.When citing, please reference the published version.Take down policyWhile the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has beenuploaded in error or has been deemed to be commercially or otherwise sensitive.If you believe that this is the case for this document, please contact UBIRA@lists.bham.ac.uk providing details and we will remove access tothe work immediately and investigate.Download date: 01. Mar. 2020 A Broadband Zoned Fishnet Metamaterial Lens  B. Orazbayev(1), V. Pacheco-Peña (1), M. Beruete(1), M. Navarro-Cía*(2) (1) Universidad Pública de Navarra, Pamplona 31006, Spain, miguel.beruete@unavarra.es (2) Imperial College London, London SW7 2AZ, UK, m.navarro@imperial.ac.uk  Lenses, as optical instruments, have been known for centuries. With the appearance of Kock’s metallic lenses, and later metamaterials, which allow tailoring both permittivity and permeability, the lenses have gained a renewed look. This great deal of effort has paid off resulting in perfect lenses, superlenses, hyperbolic lenses, chiral lenses, transformation optics lenses, epsilon-near-zero lenses, etc. One of the promising practical realizations of a metamaterial lens is the fishnet metamaterial lens. Consisting of stacked subwavelength hole arrays and working in the realm of the extraordinary transmission, the fishnet metamaterial offers lower losses and frequency-robust magnetic response. Although showing a good performance, plano- and bi-concave fishnet lenses are relatively voluminous. This problem can be solved by applying the well-known zoning technique, whereby the redundant material is removed when one wavelength phase shift in it is reached. Such a technique was successfully applied in the previous works and demonstrated the reduction of the weight and absorption losses, but for single-frequency operation (V. Pacheco-Peña et al., Appl. Phys. Lett., 103, 183507, 2013; V. Pacheco-Peña et al., J. Appl. Phys., 115, 124902, 2014).   The operational band can be broadened by applying an improved zoning technique, which exploits a strong dispersion of the fishnet. A best fitting procedure, which minimizes the root-mean-square-error between the smooth analytical profile and its staircase approximation (defined by the fishnet unit cell) for the whole band, is applied to the conventional zoning technique. As a result, the optimal zoned lens profile is obtained. It should be noticed that the resulting profile is completely different from that used in previous works, where it was obtained only for a single frequency.  In this communication, we present a broadband zoned fishnet lens designed by using the smart optimization procedure described above. The lens was fabricated and its performance was investigated experimentally at frequencies f1 = 54 GHz and f2 = 55.5 GHz. The results were compared against analytical calculations based on the Huygens-Fresnel principle, and full-wave numerical simulations. The results demonstrate a good agreement with the design parameters and an enhancement above 9 dB in the frequency range 54-58 GHz, while the zoned lens optimized for single-band operation achieves enhancement values above 9 dB only at the design frequency range, 55 - 56.5 GHz. The numerical and experimental results of a proposed lens antenna show directivities above 15 dB for both frequency bands. 

A broadband fishnet metamaterial lens

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A broadband fishnet metamaterial lens

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