BUSCADOR RECOLECTA

Frozen modes arising in stacked subwavelength hole arrays are studied in detail. Their origin is proved to be connected with the interaction between the extraordinary transmission resonance and the Fabry–Perot cavity mode. The analysis is done for various situations that differ in metal plate thicknesses and sizes and shape of the holes. Dispersion results and finite-stack transmission spectra are in good agreement, both showing the features indicating hybridization. The boundaries of the hybridization are found in terms of the geometrical parameters. The effect of the number of stacked plates on the transmission has been demonstrated. Finally, it is shown that the group index of refraction ng in the considered finite structures can be larger than 200. The obtained estimates of ng, which are based on dispersion and transmission results, well coincide with each other., This work was supported in part by the Spanish Government under Contract Consolider Engineering Metamaterials CSD2008-00066 and Contract TEC2011-28664-C02-01. M.B. is sponsored by the Spanish Government via RYC-2011-08221. P.R.U. is sponsored by the Government of Navarre via program “Formación de Tecnólogos” 055/01/11. M.N.C. is supported by the Imperial College Junior Research Fellowship. A.E.S. thanks Deutsche Forschungsgemeinschaft for partial support of this work under Project No. SE1409/2-2.
In memoriam of Mario Sorolla.

A general theory of reciprocal unidirectional transmission with tunable sign-switchable refraction and deflection of outgoing wave in structures with broken spatial inversion symmetry is presented. Several coupling scenarios connected with the diffraction-inspired asymmetry in transmission are considered for volumetric structures with one-side corrugations. They illustrate conditions of coexistence of diodelike unidirectional transmission and tunability of deflection and refraction, including change of their sign. Simulation results are presented and analyzed for nonsymmetric structures based on the stacked subwavelength hole array metamaterial. It is shown that one-way coupling can appear within a wide range of frequencies and angles of incidence, a part of which may be used to obtain different signs of deflection. Transmission results and field distributions confirm the possibility of obtaining high-contrast unidirectional transmission that can be tuned by varying incidence angle, while frequency is fixed. A pronounced unidirectional transmission is demonstrated at negative deflection in structures that are only 0.47λ0 thick, whereas a thicker structure is required in order to obtain both signs of deflection in a unidirectional regime., This work was sponsored by the Spanish Government and European Union funds under contracts Consolider “Engineering Metamaterials” CSD2008-00066 and TEC2011-28664-C02-01. P.R.-U. is sponsored by the Government of Navarre via the program “Formacion de Tecnólogos” 055/01/11. M.B. is sponsored by the Spanish Government via RYC-2011-08221. M.N.-C. is supported by the Imperial College Junior Research Fellowship. The contribution of A.E.S. was partially supported by the DFG, Project No. 1409/2-2, and by the European Science Foundation under the RNP NEWFOCUS program.

Invisibility in a diffusive-light-scattering medium has been recently demonstrated by employing a scattering-cancellation core-shell cloak. Unlike nondiffusive cloaks, such a device can be simultaneously macroscopic, broadband, passive, polarization independent, and omnidirectional. Unfortunately, it has been verified that this cloak, as well as more sophisticated ones based on transformation optics, fail under pulsed illumination, invalidating their use for a variety of applications. Here, we introduce a different approach based on unimodular transformations that enables the construction of unidirectional diffusive-light cloaks exhibiting a perfect invisibility effect, even under transient conditions. Moreover, we demonstrate that a polygonal cloak can extend this functionality to multiple directions with a nearly ideal behavior, while preserving all other features. We propose and numerically verify a simple cloak realization based on a layered stack of two isotropic materials. The studied devices have several applications not addressable by any of the other cloaks proposed to date, including shielding from pulse-based detection techniques, cloaking undesired scattering elements in time-of-flight imaging or high-speed communication systems for diffusive environments, and building extreme optical security features. The discussed cloaking strategy could also be applied to simplify the implementation of thermal cloaks., This work was supported in part by the Spanish Ministerio de Economia y Competitividad under Contracts No. TEC2014-51902-C2-1-R and No. TEC2014- 51902-C2-2-R. B.O. is sponsored by the Spanish Ministerio de Economia y Competitividad under Grant No. FPI BES-2012-054909. M.B. is sponsored by the Spanish Ministerio de Economia y Competitividad via Grant No. RYC-2011-08221. C.G.-M. acknowledges support from Generalitat Valenciana through the VALi+d postdoctoral program (Grant No. APOSTD/2014/044).

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 17 THz upholding unification of plasmonics and microwave concepts and allowing for a simplification of structure design and analysis; in practical terms, a broadband funnelling of infrared 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., In memoriam Prof. Mario Sorolla. Effort sponsored by Spanish Government under contracts Consolider "Engineering Metamaterials" CSD2008-00066, TEC2011-28664-C01 and TEC2011-28664-C02. V. T. acknowledges funding from Universidad Publica de Navarra. P.R.-U. is sponsored by the Government of Navarra under funding program "Formacion de tecnologos" 055/01/11. M. N.-C. is supported by the Imperial College Junior Research Fellowship. M. B. acknowledges funding by the Spanish Government under the research contract program Ramon y Cajal RYC-2011-08221.