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  • Journal article
    Cappel UB, Moia D, Bruno A, Vaissier V, Haque SA, Barnes PRFet al., 2016,

    Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    , Scientific Reports, Vol: 6, ISSN: 2045-2322

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  • Journal article
    Kafizas A, Wang X, Pendlebury SR, Barnes P, Ling M, Sotelo-Vazquez C, Quesada-Cabrera R, Li C, Parkin IP, Durrantt JRet al., 2016,

    Where Do Photogenerated Holes Go in Anatase:Rutile TiO2? A Transient Absorption Spectroscopy Study of Charge Transfer and Lifetime

    , JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 120, Pages: 715-723, ISSN: 1089-5639
  • Journal article
    Zhao W, Wang S, Liu B, Verzhbitskiy I, Li S, Giustiniano F, Kozawa D, Loh KP, Matsuda K, Okamoto K, Oulton RF, Eda Get al., 2016,

    Exciton-Plasmon Coupling and Electromagnetically Induced Transparency in Monolayer Semiconductors Hybridized with Ag Nanoparticles

    , Advanced Materials, Vol: 28, Pages: 2709-2715, ISSN: 1521-4095
  • Journal article
    Wilkinson JT, Whitehouse CB, Oulton RF, Gennaro SDet al., 2016,

    An undergraduate experiment demonstrating the physics of metamaterials with acoustic waves and soda cans

    , American Journal of Physics, Vol: 84, Pages: 14-20, ISSN: 0002-9505

    We describe a novel undergraduate research project that highlights the physics of metamaterials withacoustic waves and soda cans. We confirm the Helmholtz resonance nature of a single can bymeasuring its amplitude and phase response to a sound wave. Arranging multiple cans in arrayssmaller than the wavelength, we then design an antenna that redirects sound into a preferred direction.The antenna can be thought of as a new resonator, composed of artificially engineered meta-atoms,similar to a metamaterial. These experiments are illustrative, tactile, and open ended so as to enablestudents to explore the physics of matter/wave interaction

  • Journal article
    Nielsen MP, Lafone L, Rakovich A, Sidiropoulos TP, Rahmani M, Maier SA, Oulton RFet al., 2016,

    Adiabatic Nanofocusing in Hybrid Gap Plasmon Waveguides on the Silicon-on-Insulator Platform.

    , Nano Letters, Vol: 16, Pages: 1410-1414, ISSN: 1530-6992

    We present an experimental demonstration of a new class of hybrid gap plasmon waveguides on the silicon-on-insulator (SOI) platform. Created by the hybridization of the plasmonic mode of a gap in a thin metal sheet and the transverse-electric (TE) photonic mode of an SOI slab, this waveguide is designed for efficient adiabatic nanofocusing simply by varying the gap width. For gap widths greater than 100 nm, the mode is primarily photonic in character and propagation lengths can be many tens of micrometers. For gap widths below 100 nm, the mode becomes plasmonic in character with field confinement predominantly within the gap region and with propagation lengths of a few microns. We estimate the electric field intensity enhancement in hybrid gap plasmon waveguide tapers at 1550 nm by three-photon absorption of selectively deposited CdSe/ZnS quantum dots within the gap. Here, we show electric field intensity enhancements of up to 167 ± 26 for a 24 nm gap, proving the viability of low loss adiabatic nanofocusing on a commercially relevant photonics platform.

  • Conference paper
    Shibanuma T, Albella P, Maier SA, 2016,

    Efficient directional control of scattered field at optical frequency with subwavelength asymmetric dielectric dimers

    , 10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS), Publisher: IEEE, Pages: 331-333
  • Journal article
    Duffin TJ, Nielsen MP, Diaz F, Palomba S, Maier SA, Oulton RFet al., 2015,

    Degenerate four-wave mixing in silicon hybrid plasmonic waveguides

    , Optics Letters, Vol: 41, Pages: 155-158, ISSN: 1539-4794

    Silicon-based plasmonic waveguides show high confinementwell beyond the diffraction limit. Various deviceshave been demonstrated to outperform their dielectriccounterparts at micrometre scales, such as linearmodulators, capable of generating high field confinementand improving device efficiency by increasingaccess to nonlinear processes, limited by ohmiclosses. By using hybridised plasmonic waveguide architecturesand nonlinear materials, silicon-based plasmonicwaveguides can generate strong nonlinear effectsover just a few wavelengths. We have theoreticallyinvestigated the nonlinear optical performance of twohybrid plasmonic waveguides (HPWG) with three differentnonlinear materials. Based on this analysis, thehybrid gap plasmon waveguide (HGPW), combinedwith the DDMEBT nonlinear polymer, shows a fourwavemixing (FWM) conversion efficiency of 16.4dBover a 1mm propagation length, demonstrating that plasmonicwaveguides can be competitive with standardsilicon photonics structures over distances three ordersof magnitude shorter.

  • Journal article
    Burn DM, Chadha M, Branford WR, 2015,

    Angular-dependent magnetization reversal processes in artificial spin ice

    , Physical Review B - Condensed Matter and Materials Physics, Vol: 92, ISSN: 1098-0121

    The angular dependence of the magnetization reversal in interconnected kagome artificial spin ice structures has been studied through experimental MOKE measurements and micromagnetic simulations. This reversal is mediated by the propagation of magnetic domain walls along the interconnecting bars, which either nucleate at the vertex or arrive following an interaction in a neighboring vertex. The physical differences in these processes show a distinct angular dependence allowing the different contributions to be identified. The configuration of the initial magnetization state, either locally or on a full sublattice of the system, controls the reversal characteristics of the array within a certain field window. This shows how the available magnetization reversal routes can be manipulated and the system can be trained.

  • Journal article
    Levy U, Berini P, Maier SA, Mortensen NAet al., 2015,

    Focus Issue on surface plasmon photonics introduction

    , OPTICS EXPRESS, Vol: 23, Pages: 32075-32079, ISSN: 1094-4087
  • Journal article
    Albella P, Shibanuma T, Maier S, 2015,

    Switchable directional scattering of electromagnetic radiation with subwavelength asymmetric silicon dimers

    , Scientific Reports, Vol: 5, ISSN: 2045-2322

    High refractive index dielectric nanoparticles show high promise as a complementary nanophotonics platform due to compared with plasmonic nanostructures low absorption losses and the co-existence of magnetic and electric resonances. Here we explore their use as resonantly enhanced directional scatterers.We theoretically demonstrate that an asymmetric dimer of silicon nanoparticles shows tuneable directional scattering depending on the frequency of excitation. This is due to the interference between dipoles excited in each nanoparticle, enabling directional control of the scattered light. Interestingly, this control can be achieved regardless of the polarization direction with respect to the dimer axis; however, difference in the polarization can shift the wavelengths at which the directional scattering is achieved. We also explore the application of such an asymmetric nanoantenna as a tuneable routing element in a nanometer scale a full numerical simulation, suggesting applications in optical nanocircuitry.

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