Open Access
Experimental demonstration of metasurface-based ultrathin carpet cloaks for millimetre waves
(Wiley, 2016) Orazbayev, Bakhtiyar; Mohammadi Estakhri, Nasim; Alù, Andrea; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A metasurface carpet cloak for millimeter-wave range with polarization-independent performance is experimentally demonstrated. It is shown that the cloak is able to mimic the ground plane by fully restoring the amplitude and phase distributions for both transverse electric and transverse magnetic polarizations, with a relatively wide frequency and angular widths response.
Open Access
All-metallic ε-near-zero (ENZ) lens based on ultra-narrow hollow rectangular waveguides: experimental results
(IEEE, 2014) Orazbayev, Bakhtiyar; Torres Landívar, Víctor; Pacheco-Peña, Víctor; Falcone Lanas, Francisco; Teniente Vallinas, Jorge; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Navarro Cía, Miguel; Engheta, Nader; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Here we perform numerical and experimental investigation of plano-concave all-metallic ε-near-zero (ENZ) lens with operational frequency f = 144 GHz. The ENZ lens is achieved by stacking an array of narrow hollow rectangular waveguides working near cut-off frequency. Focusing and radiation properties are numerically analyzed and measured. The enhancement of 5.61 dB and directivity of 17.6 dBi are shown. Good agreement between experimental and numerical results is demonstrated.
Open Access
Ultra-compact planoconcave zoned metallic lens based on the fishnet metamaterial
(AIP Publishing, 2013) Pacheco-Peña, Víctor; Orazbayev, Bakhtiyar; Torres Landívar, Víctor; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
A 1.5λ0 -thick planoconcave zoned lens based on the fishnet metamaterial is demonstrated experimentally at millimeter wavelengths. The zoning technique applied allows a volume reduction of 60% compared to a full fishnet metamaterial lens without any deterioration in performance. The structure is designed to exhibit an effective refractive index n = -0.25 at f = 56.7GHz (λ0 = 5.29 mm) with a focal length FL = 47.62 mm = 9λ0. The experimental enhancement achieved is 11.1dB, which is in good agreement with simulation and also with previous full fishnet metamaterial lenses and opens the door for integrated solutions.
Open Access
Soret fishnet metalens antenna
(Springer Nature, 2015) Orazbayev, Bakhtiyar; Beruete Díaz, Miguel; Pacheco-Peña, Víctor; Crespo López, Gonzalo; Teniente Vallinas, Jorge; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
At the expense of frequency narrowing, binary amplitude-only diffractive optical elements emulate refractive lenses without the need of large profiles. Unfortunately, they also present larger Fresnel reflection loss than conventional lenses. This is usually tackled by implementing unattractive cumbersome designs. Here we demonstrate that simplicity is not at odds with performance and we show how the fishnet metamaterial can improve the radiation pattern of a Soret lens. The building block of this advanced Soret lens is the fishnet metamaterial operating in the near-zero refractive index regime with one of the edge layers designed with alternating opaque and transparent concentric rings made of subwavelength holes. The hybrid Soret fishnet metalens retains all themeritsof classicalSoret lenses suchas lowprofile, lowcost andeaseofmanufacturing. It is designed for the W-band of themillimeter-waves range with a subwavelength focal lengthFL51.58 mm(0.5l0) aiming at a compact antenna or radar systems. The focal properties of the lens along with its radiation characteristics in a lens antenna configuration have been studied numerically and confirmed experimentally, showing a gain improvement of ,2 dB with respect to a fishnet Soret lens without the fishnet metamaterial.
Open Access
Mechanical 144GHz beam steering with all-metallic epsilon-near-zero lens antenna
(AIP Publishing, 2014) Pacheco-Peña, Víctor; Torres Landívar, Víctor; Orazbayev, Bakhtiyar; Beruete Díaz, Miguel; Navarro Cía, Miguel; Sorolla Ayza, Mario; Engheta, Nader; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
An all-metallic steerable beam antenna composed of an ε-near-zero (ENZ) metamaterial lens is experimentally demonstrated at 144 GHz (λ0 = 2.083 mm). The ENZ lens is realized by an array of narrow hollow rectangular waveguides working just near and above the cut-off of the TE10 mode. The lens focal arc on the xz-plane is initially estimated analytically as well as numerically and compared with experimental results demonstrating good agreement. Next, an open-ended waveguide is placed along the lens focal arc to evaluate the ENZ-lens antenna steerability. A gain scan loss below 3 dB is achieved for angles up to plus/minus 15º.
Open Access
Zoned near-zero refractive index fishnet lens antenna: steering millimeter waves
(AIP Publishing, 2014) Pacheco-Peña, Víctor; Orazbayev, Bakhtiyar; Beaskoetxea Gartzia, Unai; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A zoned fishnet metamaterial lens is designed, fabricated, and experimentally demonstrated at millimeter wavelengths to work as a negative near-zero refractive index lens suitable for compact lens antenna configurations. At the design frequency f=56.7GHz (wavelength = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL= 9 wavelengths, exhibits a refractive index n = 0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7 dB, corresponding to a gain of 12.26 dB. Moreover, beam steering capability of the structure by shifting the feeder on the xz-plane is demonstrated.
Open Access
Metamaterials for enhanced light control: from high resolution focusing to invisibity
(2015) Orazbayev, Bakhtiyar; Beruete Díaz, Miguel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa
Artificial dielectrics and their descendants – metamaterials, have unusual electromagnetic parameters and provide more abilities than naturally available dielectrics for control of the light. The first experimental realization of a double negative medium gave an enormous impulse for research in the field of electromagnetism. As result, a lot of fascinating electromagnetic devices have been developed since then, including metamaterial lenses, beam steerers and even invisibility cloaks. The aim of this master thesis is to contribute to the development of such devices, especially metamaterial lenses and invisibility cloaks. First, a background of metamaterial and metasurfaces is introduced. The main aspects of metamaterials and their characteristics are reviewed, so that the working principles of metamaterials can be acquired with minimal prerequisite mathematics. Then we review the design process of several metamaterial lenses, including a zoned fishnet metamaterial lens and a Soret lens, a member of Fresnel zone plate lenses. Finally we design a carpet cloak, using a metasurface with double ring resonators. In the first application, the time-honored zoning technique is used to reduce the volume, and therefore weight, of a fishnet metamaterial lens. By properly optimizing a profile of the zoned lens we are able to reduce a volume of the lens up to 60% and broaden the fractional bandwidth up to 3 times. With this optimization technique the bandwidth of the zoned lens, which usually is narrow band, increases without causing any deterioration in its performance. The second metamaterial lens is a member of the well-known Fresnel zone plate’s family and consists of alternating and opaque concentric rings. Since half of the power is blocked by opaque rings the efficiency of such lenses is low. In order to improve the coupling and illumination efficiency we propose using an array of subwavelength holes instead of the transparent ring. Also by supporting the lens with a block of fishnet metamaterial working in near-zero index regime it is possible to improve radiation characteristics of a metalens antenna, such as directivity and side lobe level. Finally, in the third application a ground cloak design is described as simulation results. The presented ground cloak is based on a metasurface, an array of closed ring resonators, and, therefore, has an ultrathin design and relatively simple in fabrication. The proposed cloak has been successfully employed to conceal an electrically large object (1.1λ0) for wide range of incident angles and relatively wide frequency range.
Open Access
Experimental demonstration of a millimeter-wave metallic ENZ lens based on the energy squeezing principle
(IEEE, 2015) Torres Landívar, Víctor; Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Teniente Vallinas, Jorge; Beruete Díaz, Miguel; Navarro Cía, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The performance of an epsilon-near zero (ENZ) plano-concave lens is experimentally demonstrated and verified at the D-band of the millimeter-waves. The lens is comprised of an array of narrow metallic waveguides near cut-off frequency, which effectively behaves as an epsilon-near-zero medium at 144 GHz. A good matching with free space is achieved by exploiting the phenomenon of energy squeezing and a clear focus with a transmission enhancement of 15.9 dB is measured. The lens shows good radiation properties with a directivity of 17.6 dBi and low cross-polar components of -34 dB. All results are supported by numerical simulations.
Open Access
Tunable beam steering enabled by graphene metamaterials
(Optical Society of America, 2016) Orazbayev, Bakhtiyar; Beruete Díaz, Miguel; Khromova, Irina; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We demonstrate tunable mid-infrared (MIR) beam steering devices based on multilayer graphene-dielectric metamaterials. The effective refractive index of such metamaterials can be manipulated by changing the chemical potential of each graphene layer. This can arbitrarily tailor the spatial distribution of the phase of the transmitted beam, providing mechanisms for active beam steering. Three different beam steerer (BS) designs are discussed: a graded-index (GRIN) graphene-based metamaterial block, an array of metallic waveguides filled with graphene-dielectric metamaterial and an array of planar waveguides created in a graphene-dielectric metamaterial block with a specific spatial profile of graphene sheets doping. The performances of the BSs are numerically analyzed, showing the tunability of the proposed designs for a wide range of output angles (up to approximately 70°). The proposed graphene-based tunable beam steering can be used in tunable transmitter/receiver modules for infrared imaging and sensing.
Open Access
Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens
(Optical Society of America, 2015) Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Metamaterial lenses with close values of permittivity and permeability usually display low reflection losses at the expense of narrow single frequency operation. Here, a broadband low-profile lens is designed by exploiting the dispersion of a fishnet metamaterial together with the zoning technique. The lens operates in a broadband regime from 54 GHz to 58 GHz, representing a fractional bandwidth ~7%, and outperforms Silicon lenses between 54 and 55.5 GHz. This broadband operation is demonstrated by a systematic analysis comprising Huygens-Fresnel analytical method, full-wave numerical simulations and experimental measurements at millimeter waves. For demonstrative purposes, a detailed study of the lens operation at two frequencies is done for the most important lens parameters (focal length, depth of focus, resolution, radiation diagram). Experimental results demonstrate diffraction-limited ~0.5λ transverse resolution, in agreement with analytical and numerical calculations. In a lens antenna configuration, a directivity as high as 16.6 dBi is achieved. The different focal lengths implemented into a single lens could be potentially used for realizing the front end of a non-mechanical zoom millimeter-wave imaging system.