Open Access
Mid-infrared plasmonic inductors: enhancing inductance with meandering lines
(Nature Publishing Group, 2014) Torres Landívar, Víctor; Ortuño Molinero, Rubén; Rodríguez Ulibarri, Pablo; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Griol, Amadeu; Martínez, Alejandro; Navarro Cía, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua: 055/01/11; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a mid-infrared inductor that when applied to an extraordinary transmission hole array produces a strong redshift of the resonant peak accompanied by an unprecedented enlargement of the operation bandwidth. The importance of the result is twofold: from a fundamental viewpoint, the direct applicability of equivalent circuit concepts borrowed from microwaves is demonstrated, in frequencies as high as 17â€...THz upholding unification of plasmonics and microwave concepts and allowing for a simplification of structure design and analysis; in practical terms, a broadband funnelling ofinfrared radiation with fractional bandwidth and efficiency as high as 97% and 48%, respectively, is achieved through an area less than one hundredth the squared wavelength, which leads to an impressive accessible strong field localization that may be of great interest in sensing applications.
Open Access
Localized photonic jets from flat, three-dimensional dielectric cuboids in reflection mode
(Optical Society of America, 2015) Minin, Igor V.; Minin, Oleg V.; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A photonic jet (a terajet at terahertz frequencies) commonly denotes a specific, spatially localized region in the near field on the front side of a dielectric particle with a diameter comparable with the wavelength illuminated by a plane wave on its back side (i.e., the jet emerges from the shadow surface of a dielectric particle). In this Letter, the formation of a photonic jet is demonstrated using the recently proposed three-dimensional (3D) dielectric cuboids working in the “reflection” mode when the specific, spatially localized region is localized in the direction of the incident wavefront. The results of the simulations based on the Finite Integration Technique are discussed. All dimensions are given in wavelength units so that all results can be scaled to any frequency of interest, including optical frequencies, thus simplifying the fabrication process compared with spherical dielectrics. The results presented here may be of interest for novel applications, including microscopy techniques and sensors.
Open Access
Increasing surface plasmons propagation via photonic nanojets with periodically spaced 3D dielectric cuboids
(MDPI, 2016) Pacheco-Peña, Víctor; Minin, Igor V.; Minin, Oleg V.; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
A structure based on periodically arranged 3D dielectric cuboids connected by photonic nanojets (PNJs) is proposed with the aim of increasing the propagation distance of surface plasmon polaritons (SPPs) at the telecom wavelength of 1550 nm. The performance of the structure is evaluated and compared with the case without the cuboids demonstrating that the SPPs propagation length is enhanced by a factor greater than 2, reaching a value of approximately 190, when the gap between the cuboids is 2.50. Also, the dependence of the propagation length with the height of the cubes is evaluated, showing that this parameter is critical for a good performance of the chain. A subwavelength resolution is obtained for all the jets generated at the output of the cuboids.
Open Access
Epsilon-near-zero metalenses operating in the visible
(Elsevier, 2016) Pacheco-Peña, Víctor; Navarro Cía, Miguel; Beruete Díaz, Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Several converging lenses working in the permittivity near to zero (ENZ) regime at optical frequencies are designed using an array of metal-dielectric-metal plasmonic waveguides. These plasmonic waveguides show a dispersive nature that enable to mimic an effective ENZ medium when using the fast wave transverse electric (TE1) mode near its cut-off wavelength. By arranging multiple plasmonic waveguides with the correct engineered dimensions, several metalenses, including graded index (GRIN) ones, and diffractive optical elements (i.e., zoned metalenses) are proposed. The metalenses are designed at l0 = 474.9nm (f = 631.67THz) with a focal length of 10.75l0. Numerical results demonstrate that the best performance is obtained for the case of the GRIN metalens in terms of the focal position, transversal resolution and thickness, reducing its volume up to ∼52.3% with respect to the smooth-profiled plano-concave metalens.
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
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
Negative refraction through an extraordinary transmission left-handed metamaterial slab
(American Physical Society, 2009) Beruete Díaz, Miguel; Navarro Cía, Miguel; Sorolla Ayza, Mario; Campillo, Igor; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work we present numerical and experimental results of negative refraction through a negative index metamaterial based on miniaturized extraordinary transmission stacked subwavelength hole arrays, also known as stacked fishnet structures, working in the millimeter wave range. Analytical transmittance as a function of frequency and tangential momentum shows the conditions under which negative refraction is expected. Due to the role of the gap-surface-plasmon-polariton-like mode that gives rise to the resonant magnetic response of this structure, strong dispersion with the angle of incidence is expected. Experimental results using a quasioptical bench in the millimeter wave band demonstrate negative refraction and, besides, reasonable agreement with the simulation results is obtained. A discussion based on leaky waves serves to qualitatively explain the main features. The presented results may find application in the design of new lenses and devices both in the microwave, terahertz, and optical ranges.
Open Access
Analysis of surface-plasmon-like modes under an engineering perspective
(2011) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this communication we show how one can exploit equivalent circuits to analyze surface-plasmon-like modes (slit and hole arrays, Sievenpiper mushrooms and coaxial hole arrays) and to propose new designs with outstanding features.
Open Access
Multiband one-way polarization conversion in complementary split-ring resonator based structures by combining chirality and tunneling
(Optical Society of America, 2015) Serebryannikov, Andriy E.; Beruete Díaz, Miguel; Mutlu, Mehmet; Ozbay, Ekmel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Multiband one-way polarization conversion and strong asymmetry in transmission inspired by it are demonstrated in ultrathin sandwiched structures that comprise two twisted aperture-type arrays of complementary split-ring resonators (CSRRs), metallic mesh, and dielectric layers. The basic features of the resulting mechanism originate from the common effect of chirality and tunneling. The emphasis is put on the (nearly) perfect polarization conversion of linear incident polarization into the orthogonal one and related diodelike asymmetric transmission within multiple narrow bands. Desired polarization conversion can be obtained at several resonances for one of the two opposite incidence directions, whereas transmission is fully blocked for the other one. The resonances, at which the (nearly) perfect conversion takes place, are expected to be inherited from similar structures with parallel, i.e., not rotated CSRR arrays that do not enable chirality and, thus, polarization conversion. It is found that the basic transmission and polarization conversion features and, thus, the dominant physics are rather general, enabling efficient engineering of such structures. The lowest-frequency resonance can be obtained in structures made of conventional materials with total thickness less than λ 50/ and up to ten such resonances can correspond to thickness less than λ 20/ .
Open Access
Negative refraction in a prism made of stacked subwavelength hole arrays
(Optical Society of America, 2008) Navarro Cía, Miguel; Beruete Díaz, Miguel; Sorolla Ayza, Mario; Campillo, Igor; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Metamaterial structures are artificial materials that show unconventional electromagnetic properties such as negative refraction index, perfect lenses, and invisibility. However, losses are one of the big challenges to be surpassed in order to design practical devices at optical wavelengths. Here we report negative refraction in a prism engineered by stacked sub-wavelength hole arrays. These structures exhibit inherently an extraordinary optical transmission which could offer a solution to the problem of losses at optical wavelengths. It is shown the possibility to obtain negative indices of refraction starting from near to zero values. Our work demonstrates by a direct experiment the feasibility of engineering negative refraction by just drilling sub-wavelength holes in metallic plates and stacking them.