Open Access
Doubling the propagation distance of surface plasmon polaritons
(SPIE, 2016) Pacheco-Peña, Víctor; Minin, Igor V.; Minin, Oleg V.; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A novel passive repeater, based on a chain of 3D dielectric particles, has been proposed and numerically simulated.
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
ε-near-zero (ENZ) graded index quasi-optical devices: steering and splitting millimeter waves
(IOP Publishing, 2014) Pacheco-Peña, Víctor; Torres Landívar, Víctor; Beruete Díaz, Miguel; Navarro Cía, Miguel; Engheta, Nader; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Graded index ε near-zero (GRIN-ENZ) quasi-optical components such as beam steerers and power splitters are designed, simulated and analyzed. The GRIN-ENZ medium is realized using stacked narrow hollow waveguides whose infinite array shows the first transmission peak at 1.0002 THz. Several GRIN-ENZ beam steerers to channel a normal incident plane wave to different output angles (15, 45, 65 and 80 deg) with good impedance matching (low reflection) are analytically and numerically demonstrated using planar structures with a thickness of 5λ0 = 1500 μm along z-axis. Moreover, symmetrical and asymmetrical power splitters are designed with output angles (plus/minus 45 deg) and (-80, +35 deg), respectively.
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
Terajets produced by dielectric cuboids
(AIP Publishing, 2014) Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Minin, Igor V.; Minin, Oleg V.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The capability of generating terajets using three-dimensional (3D) dielectric cuboids working at terahertz (THZ) frequencies (as analogues of nanojets in the infrared band) is introduced and studied numerically. The focusing performance of the terajets is evaluated in terms of the transversal full width at half maximum (FWHM) along x- and y-directions using different refractive indices for a 3D dielectric cuboid with a fixed geometry, obtaining a quasi-symmetric terajet with a subwavelength resolution of 0.46 wavelengths when the refractive index is n=1.41. Moreover, the backscattering enhancement produced when metal particles are introduced in the terajet region is demonstrated for a 3D dielectric cuboid and compared with its two-dimensional (2D) counterpart. The results of the jet generated for the 3D case are experimentally validated at sub-THZ waves, demonstrating the ability to produce terajets using 3D cuboids.
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
Experimental realization of an epsilon-near-zero graded-index metalens at terahertz frequencies
(American Physical Society, 2017) Pacheco-Peña, Víctor; Engheta, Nader; Kuznetsov, Sergei A.; Gentselev, Alexandr; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The terahertz band has been historically hindered by the lack of efficient generators and detectors, but a series of recent breakthroughs have helped to effectively close the “terahertz gap.” A rapid development of terahertz technology has been possible thanks to the translation of revolutionary concepts from other regions of the electromagnetic spectrum. Among them, metamaterials stand out for their unprecedented ability to control wave propagation and manipulate electromagnetic response of matter. They have become a workhorse in the development of terahertz devices such as lenses, polarizers, etc., with fascinating features. In particular, epsilon-near-zero (ENZ) metamaterials have attracted much attention in the past several years due to their unusual properties such as squeezing, tunneling, and supercoupling where a wave traveling inside an electrically small channel filled with an ENZ medium can be tunneled through it, reducing reflections and coupling most of its energy. Here, we design and experimentally demonstrate an ENZ graded-index (GRIN) metamaterial lens operating at terahertz with a power enhancement of 16.2 dB, using an array of narrow hollow rectangular waveguides working near their cutoff frequencies. This is a demonstration of an ENZ GRIN device at terahertz and can open the path towards other realizations of similar devices enabling full quasioptical processing of terahertz signals.
Open Access
Metamaterials and plasmonics applied to devices based on periodic structures at high frequencies: microwaves, terahertz and optical range
(2016) Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Esta tesis muestra el trabajo de investigación desarollado bajo el programa de doctorado “tecnología de las comunicaciones” de la Universidad Pública de Navarra (UPNA), para el grado de Doctor (PhD) en Ingenieria de Telecomunicaciones. La guía, supervisión y dirección de esta tesis doctoral ha sido desarrollada por Dr. Miguel Beruete Díaz de la UPNA. Durante el programa de PhD, dos estancias internacionales han sido completadas por este estudiante doctoral en las siguientes instituciones: Universidad de Pennsylvania bajo la supervisión de Prof. Nader Engheta (3 meses) y Imperial College London bajo la guía de Dr. Miguel Navarro-Cía (2 meses). Los temas tratados en esta tesis son desarrollados en milimétricas, terahercios y frecuencias ópticas. Se usan principalmente metamateriales y estructuras periódicas en el diseño de diferentes dispositivos como lentes, direccionadores de haz, guías de onda, etc.
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.
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.