A broadband fishnet metamaterial lens

B. Orazbayev, V. Pacheco-Peña, M. Beruete, Miguel Navarro-Cia

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Abstract

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 abricated
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.
Original languageEnglish
Title of host publicationIEEE AP-S International Symposium on Antennas and Propagation 2015 and USNC/URSI National Radio Science Meeting 2015 (2015 IEEE AP-S/URSI), Vancouver, Canada, July (2015)
Pages1
Number of pages1
Publication statusUnpublished - 2015

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