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  • Journal article
    Gennaro SD, Roschuk TR, Maier SA, Oulton RFet al., 2016,

    Measuring chromatic aberrations in imaging systems using plasmonic nanoparticles

    , Optics Letters, Vol: 41, Pages: 1688-1691, ISSN: 1539-4794

    We demonstrate a method to measure chromatic aberrations of microscope objectives with metallic nanoparticles using white light. Extinction spectra are recorded while scanning a single nanoparticle through a lens’s focal plane. We show a direct correlation between the focal wavelength and the longitudinal chromatic focal shift through our analysis of the variations between the scanned extinction spectra at each scan position and the peak extinction over the entire scan. The method has been tested on achromat and apochromat objectives using aluminum disks varying in size from 260–520 nm. Our method is straightforward, robust, low cost, and broadband with a sensitivity suitable for assessing longitudinal chromatic aberrations in high-numerical-aperture apochromatic corrected lenses.

  • Journal article
    Roeder R, Sidiropoulos TPH, Buschlinger R, Riediger M, Peschel U, Oulton RF, Ronning Cet al., 2016,

    Mode Switching and Filtering in Nanowire Lasers

    , Nano Letters, Vol: 16, Pages: 2878-2884, ISSN: 1530-6992

    Coherent light sources confining the light below the vacuum wavelength barrier will drive future concepts of nanosensing, nanospectroscopy, and photonic circuits. Here, we directly image the angular emission of such a light source based on single semiconductor nanowire lasers. It is confirmed that the lasing switches from the fundamental mode in a thin ZnO nanowire to an admixture of several transverse modes in thicker nanowires approximately at the multimode cutoff. The mode competition with higher order modes substantially slows down the laser dynamics. We show that efficient photonic mode filtering in tapered nanowires selects the desired fundamental mode for lasing with improved performance including power, efficiency, and directionality important for an optimal coupling between adjacent nanophotonic waveguides.

  • Journal article
    Bak AO, Yoxall EO, Sarriugarte P, Giannini V, Maier SA, Hillenbrand R, Pendry JB, Phillips CCet al., 2016,

    Harnessing a Quantum Design Approach for Making Low-Loss Superlenses

    , NANO LETTERS, Vol: 16, Pages: 1609-1613, ISSN: 1530-6984
  • 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.

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