Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass

Metallic nanowires (NW) coated with a high permittivity dielectric are proposed as means to strongly reduce the light scattering of the conducting NW, rendering them transparent at infrared wavelengths of interest in telecommunications. Based on a simple, universal law derived from electrostatics arguments, we find appropriate parameters to reduce the scattering efficiency of hybrid metal-dielectric NW by up to three orders of magnitude as compared with the scattering efficiency of the homogeneous metallic NW. We show that metal@dielectric structures are much more robust against fabrication imperfections than analogous dielectric@metal ones. The bandwidth of the transparent region entirely covers the near IR telecommunications range. Although this effect is optimum at normal incidence and for a given polarization, rigorous theoretical and numerical calculations reveal that transparency is robust against changes in polarization and angle of incidence, and also holds for relatively dense periodic or random arrangements. A wealth of applications based on metal-NWs may benefit from such invisibility

Metallo-dielectric core-shell nanospheres as building blocks for optical three-dimensional isotropic negative-index metamaterials

Materials showing electromagnetic properties that are not attainable in naturally occurring media, so-called metamaterials, have been lately, and still are, among the most active topics in optical and materials physics and engineering. Among these properties, one of the most attractive ones is the subdiffraction resolving capability predicted for media having an index of refraction of -1. Here, we propose a fully three-dimensional, isotropic metamaterial with strong electric and magnetic responses in the optical regime, based on spherical metallo-dielectric core-shell nanospheres. The magnetic response stems from the lowest, magnetic-dipole resonance of the dielectric shell with a high refractive index, and can be tuned to coincide with the plasmon resonance of the metal core, responsible for the electric response. Since the response does not originate from coupling between structures, no particular periodic arrangement needs to be imposed. Moreover, due to the geometry of the constituents, the metamaterial is intrinsically isotropic and polarization independent. It could be realized with current fabrication techniques with materials such as silver (core) and silicon or germanium (shell). For these particular realistic designs, the metamaterials present a negative index in the range of 1.2-1.55οm. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.The authors acknowledge support from the Spain Ministerio de Ciencia e Innovacion´ through the Consolider-Ingenio project EMET (CSD2008-00066) and NANOPLAS (FIS2009- 11264) and from the Comunidad de Madrid (grant MICROSERES P2009/TIC-1476). RP-D acknowledges support from CSIC through a JAE-Pre grantPeer Reviewe

Plasmon spectroscopy: Theoretical and numerical calculations, and optimization techniques

30 págs.; 22 figs.; 1 tab.; Open Access funded by Creative Commons Atribution Licence 3.0We present an overview of recent advances in plasmonics, mainly concerning theoretical and numerical tools required for the rigorous determination of the spectral properties of complex-shape nanoparticles exhibiting strong localized surface plasmon resonances (LSPRs). Both quasistatic approaches and full electrodynamic methods are described, providing a thorough comparison of their numerical implementations. Special attention is paid to surface integral equation formulations, giving examples of their performance in complicated nanoparticle shapes of interest for their LSPR spectra. In this regard, complex (single) nanoparticle configurations (nanocrosses and nanorods) yield a hierarchy of multiple-order LSPR s with evidence of a rich symmetric or asymmetric (Fano-like) LSPR line shapes. In addition, means to address the design of complex geometries to retrieve LSPR spectra are commented on, with special interest in biologically inspired algorithms. Thewealth of LSPRbased applications are discussed in two choice examples, single-nanoparticle surface-enhanced Raman scattering (SERS) and optical heating, and multifrequency nanoantennas for fluorescence and nonlinear optics.J.A.S.-G. and R.P.-D. acknowledge the Spanish >Ministerio de Economía y Competitividad>, through the Consolider-Ingenio project EMET (CSD2008- 00066) and NANOPLAS+ (FIS2012-31070), for financial support.Peer Reviewe

Fano-like interference of plasmon resonances at a single rod-shaped nanoantenna

Single metallic nanorods acting as half-wave antennas in the optical range exhibit an asymmetric, multi-resonant scattering spectrum that strongly depends on both their length and dielectric properties. Here we show that such spectral features can be easily understood in terms of Fano-like interference between adjacent plasmon resonances. On the basis of analytical and numerical results for different geometries, we demonstrate that Fano resonances may appear for such single-particle nanoantennas provided that interacting resonances overlap in both spatial and frequency domains.Comment: 18 pages, 9 figure

Resonant metal-semiconductor nanostructures as building blocks of low-loss negative- and zero-index metamaterials

5th International Conference on Metamaterials, Photonic Crystals and Plasmonics; Conferencia invitada.Here we propose a 2D isotropic metamaterial with negative electric and magnetic responses in the optical regime, based on hybrid metallo-dielectric core-shell nanowires. The magnetic response stems from the lowest magnetic resonance of the dielectric shell with high refractive index (i.e., lossless semiconductor), and can be tuned to coincide with the plasmon resonance of the metal core, responsible for the electric response. Also, the same metamaterial design is shown to yield zero refractive index for a different spectral regime (in connection with overlapping resonances), exhibiting in turn an impedance close to that of vacuum.The authors acknowledge financial support from the Spanish “Ministerio de Economía y Competitividad” (CSD2008-00066 and FIS2012-31070), and European Social Fund and CSIC (JAE-Pre and JAE-Doc grants).Peer Reviewe

Localized magnetic plasmons in all-dielectric μ<0 metastructures

6 pags.; 4 figs.; PACS number(s): 41.20.Jb, 42.70.−a, 52.40.Db, 78.67.−n© 2015 American Physical Society. Metamaterials are known to exhibit a variety of electromagnetic properties nonexisting in nature. We show that an all-dielectric (nonmagnetic) system consisting of deep-subwavelength, high-permittivity resonant spheres possesses effective negative magnetic permeability (dielectric permittivity being positive and small). Due to the symmetry of the electromagnetic wave equations in classical electrodynamics, localized >magnetic> plasmon resonances can be excited in a metasphere made of such metamaterial. This is theoretically demonstrated by the coupled-dipole approximation and numerically for real spheres, in full agreement with the exact analytical solution for the scattering process by the same metasphere with effective material properties predicted by effective medium theory. The emergence of this phenomenon as a function of structural order within the metastructures is also studied. Universal conditions enabling effective negative magnetic permeability relate subwavelength sphere permittivity and size with critical filling fraction. Our proposal paves the way towards (all-dielectric) magnetic plasmonics, with a wealth of fascinating applications.This work was supported by the Spanish MINECO (FIS2012- 31070 and FIS2012-36113) and Consolider-Ingenio EMET (CSD2008-00066).Peer Reviewe

Localized magnetic plasmons in all-dielectric \ensuremath{\mu}<0 metastructures

Metamaterials are known to exhibit a variety of electromagnetic properties nonexisting in nature. We show that an all-dielectric (nonmagnetic) system consisting of deep-subwavelength, high-permittivity resonant spheres possesses effective negative magnetic permeability (dielectric permittivity being positive and small). Due to the symmetry of the electromagnetic wave equations in classical electrodynamics, localized “magnetic” plasmon resonances can be excited in a metasphere made of such metamaterial. This is theoretically demonstrated by the coupled-dipole approximation and numerically for real spheres, in full agreement with the exact analytical solution for the scattering process by the same metasphere with effective material properties predicted by effective medium theory. The emergence of this phenomenon as a function of structural order within the metastructures is also studied. Universal conditions enabling effective negative magnetic permeability relate subwavelength sphere permittivity and size with critical filling fraction. Our proposal paves the way towards (all-dielectric) magnetic plasmonics, with a wealth of fascinating applications

The probiotic strain Shewanella putrefaciens Pdp11 strongly modulates gene expression of the fish pathogen Vibrio harveyi

In this work, the interaction between the fish probiotic Shewanella putrefaciens Pdp11 and the fish pathogen V. harveyi was studied by RNA-seq to understand how SpPdp11 interferes with the pathogen through bioinformatics analysis. Three types of cultures were performed: SpPdp11 alone, V. harveyi alone and SpPdp11 and V. harveyi together. RNA was extracted and sequenced (paired end, 2x75 bp) at the Ultrasequencing Service of the University of Málaga using the Illumina NextSeqTM 550 platform. Raw reads were processed using a bioinformatic pipeline and a network analysis was performed for the most relevant functional enrichment results. The results suggest that the presence of SpPdp11 affects V. harveyi to a greater extent than V. harveyi affects SpPdp11. Considering that V. harveyi is a pathogenic strain and SpPdp11 is a probiotic strain, this may be positive for its probiotic capacity, as it not only maintains its functionality almost intact, but also produces a huge imbalance in that of V. harveyiThis work was funded by project AG-2017-509 83370-C3-3-R (MINECO, Spain)

Silicon Mie Resonators for Highly Directional Light Emission from monolayer MoS2

Controlling light emission from quantum emitters has important applications ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries, such as wires and spheres, support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state, and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a Si nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a Si nanowire

High-efficiency and low-loss gallium nitride dielectric metasurfaces for nanophotonics at visible wavelengths

The dielectric nanophotonics research community is currently exploring transparent material platforms (e.g., TiO2, Si3N4, and GaP) to realize compact high efficiency optical devices at visible wavelengths. Efficient visible-light operation is key to integrating atomic quantum systems for future quantum computing. Gallium nitride (GaN), a III-V semiconductor which is highly transparent at visible wavelengths, is a promising material choice for active, nonlinear, and quantum nanophotonic applications. Here, we present the design and experimental realization of high efficiency beam deflecting and polarization beam splitting metasurfaces consisting of GaN nanostructures etched on the GaN epitaxial substrate itself. We demonstrate a polarization insensitive beam deflecting metasurface with 64% and 90% absolute and relative efficiencies. Further, a polarization beam splitter with an extinction ratio of 8.6/1 (6.2/1) and a transmission of 73% (67%) for p-polarization (s-polarization) is implemented to demonstrate the broad functionality that can be realized on this platform. The metasurfaces in our work exhibit a broadband response in the blue wavelength range of 430-470 nm. This nanophotonic platform of GaN shows the way to off- and on-chip nonlinear and quantum photonic devices working efficiently at blue emission wavelengths common to many atomic quantum emitters such as Ca+ and Sr+ ions. © 2017 Author(s)