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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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)
Number of pages1
Publication statusUnpublished - 2015


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