Polarization - Selective Optical Darkness in Metamaterials built from Nano-Bismuth

META'15, City College of New York, New York City, NY, USA August 4, 2015 – August 7, 2015; http://metaconferences.org/ocs/index.php/META15/META15We extend the concept of polarization ¿ selective optical darkness to metamaterials based on bismuth nanostructures (nano-Bi). It will be shown that in nano-Bi based metamaterials, this phenomenon can be achieved due to the near UV ¿ visible polaritonic resonances permitted by the near IR interband transitions of Bi.Financial support from the European Commission (FP7 STREP BisNano Project), the Spanish Ministry for Economy and Competitiveness (TEC2012-38901-C02-01 AMALIE) are acknowledged.Peer Reviewe

Linear and non-linear light emission of Er-hybridized Si nanostructures in the ultrathin geometry

Lille Grand Palais, May 11-15, 2015Resume : Advanced integrated photonic devices will include active metamaterials in which plasmonic and photonic modes will be used to manipulate the light in nanoscale dimensions. Efficient, robust, and optically modulated nanoscale light emitters with high color purity are required as active building blocks for these metamaterials. A single ultrathin layer (few nanometers thick) formed by Er ions coupled to Si nanoparticles or nanostructures (NSs) is suitable for such a purpose, since RE ions provide a robust emission that can be enhanced by using the Si NSs as sensitizers. However, it is necessary to investigate the potential of these nanoscale systems for light emission and modulation. // In this work we report the light emission properties of ultrathin (< 8 nm) hybrid Er-Si NSs layers, in which all the Er ions are located at few nm of the Si NSs in order to obtain unprecedently high sensitization efficiency. Clear IR Er light emission from an ultrathin layer containing less than 2.5% of an atomic monolayer of Er under near-ultraviolet and visible excitation. Moreover it is found that the emission of the Er-Si NSs layers shows a complex non-linear behaviour as a function of the excitation photon flux. We will discuss how these Er-Si NSs layers possess a high functional versatility, and can be used as efficient nanoscale near IR light sources the emission of which can be modulated optically. - See more at: http://www.european-mrs.com/2015-spring-symposium-h-european-materials-research-society#sthash.kww6pbzm.dpufPeer Reviewe

Optical Properties of Bismuth Nanostructures Towards the Ultrathin Film Regime

Bulk bismuth presents outstanding optical properties, such as a giant infrared refractive index (n near 10) and a negative ultraviolet visible permittivity induced by giant interband electronic transitions. Although such properties are very appealing for applications in nanophotonics, the dielectric function of bismuth nanostructures has been scarcely studied. Here, we determine by spectroscopic ellipsometry the far infrared to ultraviolet dielectric function of pulsed laser deposited bismuth thin films with nominal thickness tBi varied from near 10 nm to several tens of nm. For tBi above 15 nm, the films display a continuous structure and their dielectric function is comparable with that of bulk bismuth. For tBi below 15 nm, the film structure is discontinuous, and the dielectric function differs markedly from that of bulk bismuth. It is proposed from FDTD simulations that this marked difference arises mainly from effective medium effects induced by the discontinuous film structure, where quantum electronic confinement does not play a dominant role. This suggests that ultrathin and continuous bismuth films should present the same outstanding optical properties as bulk bismuth for high performance nanophotonic devices

Interband transitions in semi-metals, semiconductors, and topological insulators: A new driving force for plasmonics and nanophotonics

Plasmonic and Mie resonances in subwavelength nanostructures provide an efficient way to manipulate light below the diffraction limit that has fostered the growth of plasmonics and nanophotonics. Plasmonic resonances have been mainly related with the excitation of free charge carriers, initially in metals, and Mie resonances have been identified in Si nanostructures. Remarkably, although much less studied, semi-metals, semiconductors and topological insulators of the p-block enable plasmonic resonances without free charge carriers and Mie resonances with enhanced properties compared with Si. In this review, we explain how interband transitions in these materials show a major role in this duality. We evaluate the plasmonic and Mie performance of nanostructures made of relevant p-block elements and compounds, especially Bi, and discuss their promising potential for applications ranging from switchable plasmonics and nanophotonics to energy conversion, especially photocatalysis

Exploring the Optical Resonances of Photocatalytic Bismuth Nanostructures

Symposium O—Plasmonic Nanomaterials for Energy Conversion, Boston, Massachusetts, November 29-December 4, 2015Nanostructures presenting optical resonances present a strong potential for energy applications. This potential has been first developed with noble metal nanostructures. At their plasmonic resonances, they can be used as scatterers for improved light trapping into photovoltaic photonic structures or as near-field enhancers boosting photocarrier excitation in photovoltaic media.1 Very recently, plasmoelectric potentials have been measured in resonant noble metal nanostructures, thus allowing a novel opto-electrical conversion scheme.2 Optical resonances can be excited in nanostructures beyond noble metals. Indeed, most of the metals of the periodic table can support plasmonic resonances.3 Moreover, non-Drude plasmonic-like resonances can also be achieved: for instance the so-called interband polaritonic resonances in nanostructures presenting sharp interband transitions, such as bismuth nanostructures.4,5 Based on such resonances, the potential of bismuth nanostructures for photocatalysis has been demonstrated.6,7 In the reported works, photocatalysis was achieved using bismuth nanospheres. At present, the underlying mechanism has to be discussed together with the photocatalytic potential of bismuth nanostructures in a broad range of sizes and shapes. In this presentation, we provide a detailed description of the optical response of bismuth nanostructures as a function of their size and shape, with dimensions ranging from 50 nm to 500 nm. We demonstrate a strong dependence of the absorption, scattering and extinction cross-sections, near-field, surface charges and currents that will impact the efficiency of photocatalytic solutions based on bismuth nanostructures. 1 Polman, A. et al.; Photonic design principles for ultrahigh efficiency photovoltaics, Nature Materials 2012, 11, 174 2 Sheldon, M.T. et al.; Plasmoelectric potentials in metal nanostructures, Science 2014, 346, 828 3 Naik, G. et al.; Alternative plasmonic materials: Beyond gold and silver, Advanced Materials 2013, 25, 3264 4 Toudert, J. et al.; Exploring the optical potential of nano-bismuth: tunable surface plasmon resonances in the near ultraviolet-to-near infrared range, Journal of Physical Chemistry C 2012, 116, 20530 4 Toudert, J. et al.; Spectroscopic ellipsometry for active nano- and meta- materials, Nanotechnology Reviews 2014, 3, 223 6 Wang, Z. et al.; Investigation of the optical and photocatalytic properties of bismuth nanospheres prepared by a facile thermolysis method, Journal of Physical Chemistry C 2014, 118, 1155 7 Dong, F.; A semimetal bismuth element as a direct plasmonic photocatalyst, Chemical Communications 2014, 50, 10386Peer Reviewe

UV Plasmonic Metamaterial from Vertical Non-Conventional Nanoantennas

Boston, Massachusetts, November 29-December 4, 2015Metallic nanoantennas have been used as nanophotonic detectors of infrared and visible radiation [1] [2]. The extension of these elements to the ultraviolet (UV) range has not been satisfactory due to the poor optical absorption showed by metals at these frequencies. The low values of electrical conductivity of metals at UV frequencies compromise the generation of currents along the resonant geometries. In change, several non-conventional materials show a larger value of electrical conductivity, increasing notably the absorption of nanoantennas in the UV [3]. This electrical conductivity increment is more noticeable in liquid semimetals as Bismuth or Gallium. Another way to improve optical absorption of these resonant elements is to arrange them with a high spatial density of semimetal nanoantennas. In this contribution we evaluate numerically, using multiphysics simulation, the light to heat conversion performance of a vertical nanoantenna arrangement embedded in a dielectric matrix. The so-obtained UV metamaterial enabling strong electromagnetic plasmonic absorption and heating effects. The use of nanoantennas allows a polarization and frequency selectivity that can be adequate to generate ultraviolet sensors. These selectivities are strongly related with the shape of the resonant elements. Furthermore, since the vertical antennas are embedded within a robust dielectric matrix, this arrangement allows to change from solid to liquid phase maintaining the nanoantenna geometry. This is possible for materials as Bismuth or Gallium which show a lower melting temperature than dielectric substrates [4]. This phase transition makes the metamaterial active upon control of temperature. [1] L. Novotny and N. van Hulst, ¿Antennas for light,¿ Nat. Photon. 5 (2), 83-90, (2011). [2] A. Cuadrado, E. Briones, F.J. González, J. Alda, ¿Polarimetric Pixel using Seebeck Nanoantenna¿. Opt Exp, 22, No 11, 13835-13845, (2014). [3] J.Toudert, R.Serna, and M. Jiménez de Castro, ¿Exploring the optical potencial of nano-Bismuth: Tunable surface Plasmon resonances in the near Ultraviolet-to-Near Infrared range¿, J. Phys. Chem. C, 116 (38), pp 20530-20539, (2012). [4] M. Jiménez de Castro, F. Cabello, J. Toudert, R. Serna and E.Haro-Poniatowski, ¿Potential of bismuth nanoparticles embedded in a glass matrix for spectral-selective thermo-optical devices¿ Appl. Phys. Lett. 105, 113102 (2014).Peer Reviewe

Metallodielectric eutectic composite for plasmonic applications

META'15, City College of New York, New York City, NY, USA August 4, 2015 – August 7, 2015; http://metaconferences.org/ocs/index.php/META15/META15Metallodielectric composites are very interesting from the point of view of metamaterials and plasmonics. For the fabrication of self-organized metallodielectric micro/nanostructures, one particularly promising approach is based on the directional solidification of eutectics. Here we demonstrate a bulk three-dimensional nanoplasmonic eutectic composite which was obtained by bottom-up approach. This material exhibits localized surface plasmon resonance (LSPR) at visible wavelengths.The authors thank the Maestro Project 2011/02/A/ST5/00471 and the Preludium Project 2012/07/N/ST5/02428 from the National Science Centre, the Project operated within the Foundation for Polish Science Team Programme cofinanced by the EU European Regional Development Fund and the U.S. Air Force Office of Scientific Research under Grant FA9550-14-1-0061 for support of this work. Additional information: The authors have applied for a patent regarding this work.Peer Reviewe

Formamidinium Incorporation into Compact Lead Iodide for Low Band Gap Perovskite Solar Cells with Open-Circuit Voltage Approaching the Radiative Limit

To bring hybrid lead halide perovskite solar cells toward the Shockley-Queisser limit requires lowering the band gap while simultaneously increasing the open-circuit voltage. This, to some extent divergent objective, may demand the use of largecations to obtain a perovskite with larger lattice parameter together with a large crystalsize to minimize interface nonradiative recombination. When applying the two-stepmethod for a better crystal control, it is rather challenging to fabricate perovskites withFA+cations, given the small penetration depth of such large ions into a compact PbI2film. In here, to successfully incorporate such large cations, we used a high-concentration solution of the organic precursor containing small Cl-anions achieving,via a solvent annealing-controlled dissolution-recrystallization, larger than 1µmperovskite crystals in a solar cell. This solar cell, with a largely increasedfluorescencequantum yield, exhibited an open-circuit voltage equivalent to 93% of thecorresponding radiative limit one. This, together with the low band gap achieved(1.53 eV), makes the fabricated perovskite cell one of the closest to the Shockley-Queisser optimum.Peer ReviewedPostprint (author's final draft