T. J. Davis

The Commonwealth Scientific and Industrial Research Organisation, Canberra, Australian Capital Territory, Australia

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Publications (38)96.78 Total impact

  • IEEE Photonics Technology Letters 01/2014; PP(99):1-1. · 2.04 Impact Factor
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    ABSTRACT: We discuss progress in the development of asymmetric cross-shaped plasmonic antennas based on resonant nanoscale apertures surrounded by surface corrugations. By tailoring the aperture and the surrounding surface, we show directionality and polarization control of transmitted light.
    11/2013;
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    ABSTRACT: The plasmonic J-pole antenna is the nanoscale version of a radio frequency design, consisting of a half wavelength arm connected to a quarter wavelength feed pair. Here, we report on an optical J-pole antenna that displays both a dipole (1015 nm) and quadrupole resonance (653 nm). The excitation of the quadrupole resonance is optimum at an angle of incidence directly related to the geometry of the antenna, demonstrating the flexibility of the design. The J-pole antenna shows great promise for enhancing and shaping the angular emission pattern of quantum emitters.
    Applied Physics Letters 01/2013; 102(3). · 3.52 Impact Factor
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    ABSTRACT: We show theoretically and with numerical simulations that the direction of the in-plane scattering from a subwavelength optical antenna system can be controlled by the frequency of the incident light. This optical steering effect does not rely on propagation phase shifts or diffraction but arises from phase shifts in the localized surface plasmon modes of the antenna. An analytical model is developed to optimize the parameters for the configuration, showing good agreement with a rigorous numerical simulation. The simulation predicts a 25° angular shift in the direction of the light scattered from two gold nanorods for a wavelength change of 12 nm.
    Optics Letters 10/2012; 37(20):4206-8. · 3.39 Impact Factor
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    ABSTRACT: We report on a plasmonic metamaterial approach to controlling the polarisation state of visible and near infra-red (NIR) light.
    Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conference on; 01/2012
  • T.D. James, T.J. Davis, A. Roberts
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    ABSTRACT: Optical antennas have garnered much interest from the optics community for their ability to manipulate light below the diffraction limit of conventional optics. This relatively new capability to transform light at a sub-wavelength scale has been applied to quantum source enhancement, infrared detection and solar cell design. This work aims to expand upon the range of optical antennas presented in literature by exploiting the rich array of well-known radio-frequency (RF) antenna designs and applying them to the optical spectral region, for the enhancement of quantum emitters.
    Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conference on; 01/2012
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    ABSTRACT: Here we report on the integration of metallic nanorods with the phase-change material Vanadium Dioxide (VO2). The change in its optical constants that accompanies the VO2 phase transition permits the modulation of the resonant frequencies of these dipoles. This technique will underpin the development of dynamically tunable optical antennas.
    Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conference on; 01/2012
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    ABSTRACT: Quantum dot–plasmon waveguide systems are of interest for the active control of plasmon propagation, and consequently, the development of active nanophotonic devices such as nano-sized optical transistors. This paper is concerned with how varying aspect ratio of the waveguide cross-section affects the quantum dot–plasmon coupling. We compare a stripe waveguide with an equivalent nanowire, illustrating that both waveguides have a similar coupling strength to a nearby quantum dot for small waveguide cross-section, thereby indicating that stripe lithographic waveguides have strong potential use in quantum dot–plasmon waveguide systems. We also demonstrate that changing the aspect ratio of both stripe and wire waveguides can increase the spontaneous emission rate of the quantum dot into the plasmon mode, by up to a factor of five. The results of this paper will contribute to the optimisation of quantum dot–plasmon waveguide systems and help pave the way for the development of active nanophotonics devices.
    Journal of Applied Physics 10/2011; 110(7):074315-074315-6. · 2.21 Impact Factor
  • K.C. Vernon, D.E. Gomez, T.J. Davis
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    ABSTRACT: Quantum dot coupling to plasmon nanowires may enable the development of all-optical nano-scale transistors, revolutionizing integrated photonics and information processing. However positioning between the quantum dot and the nanowire is problematic. We investigate lithographic plasmon waveguides as an alternative to colloidal nanowires. In particular, we investigate the suitability of a stripe plasmon waveguide — quantum dot system. The investigation uses a numerical procedure implemented in COMSOL Multiphysics. We show that a stripe waveguide is a suitable candidate for quantum dot - plasmon coupling, with similar efficiency to the nanowire for small waveguide cross-section. We also show that by decreasing the thickness of wire and stripe waveguides it is possible to double the spontaneous emission factor.
    Conference on Lasers and Electro-Optics/Pacific Rim; 08/2011
  • K.C. Vernon, D.E. Gomez, T.J. Davis
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    ABSTRACT: Quantum dot coupling to plasmon nanowires may enable the development of all-optical nano-scale transistors, revolutionizing integrated photonics and information processing. However positioning between the quantum dot and the nanowire is problematic. We investigate lithographic plasmon waveguides as an alternative to colloidal nanowires. In particular, we investigate the suitability of a stripe plasmon waveguide — quantum dot system. The investigation uses a numerical procedure implemented in COMSOL Multiphysics. We show that a stripe waveguide is a suitable candidate for quantum dot - plasmon coupling, with similar efficiency to the nanowire for small waveguide cross-section. We also show that by decreasing the thickness of wire and stripe waveguides it is possible to double the spontaneous emission factor.
    International Quantum Electronics Conference; 08/2011
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    ABSTRACT: Electromagnetic coupling between localised plasmons on metal nanoparticles and the strong localised fields on a micro‐structured surface is demonstrated as a means to increase the enhancement factor in surface‐enhanced Raman scattering (SERS) spectroscopy. Au nanoparticles of diameter 20 nm were deposited on a micro‐structured Au surface consisting of a periodic array of square‐based pyramidal pits (Klarite). The spectra of 4‐aminothiophenol (4‐ATP) were compared before and after deposition of Au nanoparticles on the micro‐structured surface. The addition of Au nanoparticles is shown to provide significantly higher signal intensities, with improvements of the order of ∼103 per molecule compared with spectra obtained from the micro‐structured substrate alone. This hybrid approach offers promise for combining nanoparticles with micro‐ and nano‐structured surfaces in order to design SERS substrates with higher sensitivities. Copyright © 2011 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 07/2011; 43(2):196 - 201. · 2.68 Impact Factor
  • T. J. Davis, D. E. Gómez, K. C. Vernon
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    ABSTRACT: A theory of surface-enhanced Raman scattering (SERS) is developed based on the coupling between an ensemble of nanoparticles supporting localized surface-plasmon resonances (LSPRs) and a Raman-active molecule. The molecule is modeled by a dielectric particle supporting many different modes that represent its response to an applied electric field. It is shown that the modes can be modified to include the effects of the vibrational resonances of the molecule that lead to Raman scattering and the associated Stokes and anti-Stokes frequency shifts. The same theory can describe the LSPR in an ensemble of metallic nanoparticles of arbitrary shape which leads to a description of the coupling of the evanescent electric fields between the Raman-active molecule and the surface plasmons. The theory predicts the magnitudes of the SERS observed experimentally and can model many of the known Raman effects associated with the LSPR resonances in nanoparticles, including the dependence of the enhancement on the shape and geometry of the nanoparticles, and the effects of the polarization of the incident light. An analytical expression is derived for the enhancement associated with a nanoparticle ensemble that exhibits two degenerate modes and it includes an interference effect arising from the coupling between the modes and the Raman scattering from the molecule.
    Physical review. B, Condensed matter 11/2010; 82(20). · 3.66 Impact Factor
  • T J Davis, D E Gómez, K C Vernon
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    ABSTRACT: An "electrostatic" eigenmode method based on the coupling of evanescent electric fields is presented for modeling the hybridization of localized surface plasmon resonances in metallic nanoparticles of arbitrary shape. The method yields simple analytical expressions for the hybridized energies and excitation amplitudes of nanoparticle ensembles. Because of its ease of applicability and simple conceptual basis, we anticipate that the method will be of value in understanding and predicting the effects of interacting plasmonic nanoparticles.
    Nano Letters 07/2010; 10(7):2618-25. · 13.03 Impact Factor
  • D. E. Gómez, K. C. Vernon, T. J. Davis
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    ABSTRACT: We present theoretical studies on the collective optical response of symmetric configurations of metallic nanoparticles. We show that within the electrostatic approximation, the surface plasmon resonance of these symmetric multiparticle systems can be expressed as symmetry-adapted linear combinations of the plasmon modes of each particle of the ensemble, closely resembling the situation encountered in molecular systems. By making use of group theoretical arguments, we show that such linear combinations can be written down by simple geometrical considerations through the use of point group character tables, without using extensive numerical computations. Furthermore, we apply this formalism to study the coupling of hierarchical arrays containing a large number of nanoparticles. This theory thus provides an intuitive and formal approach for the rational design of plasmonic nanostructures.
    Physical review. B, Condensed matter 02/2010; 81(7). · 3.66 Impact Factor
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    ABSTRACT: We present an experimental demonstration of strong optical coupling between CdSe quantum dots of different sizes which is induced by a surface plasmon propagating on a planar silver thin film. Attenuated total reflection measurements demonstrate the hybridization of exciton states, characterized by the observation of two avoided crossings in the energy dispersion measured for the interacting system.
    Applied Physics Letters 02/2010; 96:073108--3. · 3.52 Impact Factor
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    ABSTRACT: In this paper we theoretically consider the physical mechanisms behind the surface-enhanced Raman scattering (SERS) enhancement produced by commercially available Klarite substrates, which consist of rectangular arrays of micrometre-sized pyramidal pits in silicon with a thin gold coating. Full three-dimensional numerical simulations of the pits are conducted for both a real gold metal coating and a perfect electrical conductor (PEC) to determine whether the SERS enhancement is due to diffraction or plasmon effects. The pit apex angle and metal coating thickness are also varied to determine whether it is possible to further enhance the SERS signal by optimising the structural parameters of these substrates. By decreasing the film thickness and adjusting the apex angle, it is possible to achieve an enhancement almost double that of a standard Klarite substrate. Copyright © 2010 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 01/2010; 41(10):1106 - 1111. · 2.68 Impact Factor
  • T. J. Davis, D. E. Gómez, K. C. Vernon
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    ABSTRACT: A theory is developed to model the interaction of molecules with the localized surface plasmon resonances in metallic nanoparticles that are used for single-molecule sensing. Each molecule is represented by a simple point-like dipole based on a dielectric sphere, taken in the limit of a small radius. The surface-charge and surface-dipole eigenfunctions of a small spherical particle are represented analytically and it is shown that these are natural extensions of the electrostatic coupling theory of Davis et al. Phys. Rev. B 79 155423 (2009)]. The effect of a molecule on the surface plasmon resonances is described in terms of an effective background permittivity and formulas for the frequency and phase shifts of the resonances are obtained that depend on the polarizability of the molecule, the eigenvalues associated with the nanoparticle resonances and the strength of the geometric coupling. The interaction of the point-like dipoles with surface charges of different distributions is studied and it is shown that for molecules that cannot approach closer to the nanoparticle than a fixed distance, there is an optimum dimension of the nanoparticle to obtain the maximum coupling. This is important for the optimum design of nanoparticle-based sensors. Analytical expressions for the coupling of molecules to nanoparticles are obtained for some simple geometries and the results are compared with numerical simulations.
    Physical review. B, Condensed matter 01/2010; 81(4). · 3.66 Impact Factor
  • K. C. Vernon, D. E. Gomez, T. J. Davis
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    ABSTRACT: The use of metal stripes for the guiding of plasmons is a well established technique for the infrared regime and has resulted in the development of a myriad of passive optical components and sensing devices. However, the plasmons suffer from large losses around sharp bends, making the compact design of nanoscale sensors and circuits problematic. A compact alternative would be to use evanescent coupling between two sufficiently close stripes, and thus we propose a compact interferometer design using evanescent coupling. The sensitivity of the design is compared with that achieved using a hand-held sensor based on the Kretschmann style surface plasmon resonance technique. Modeling of the new interferometric sensor is performed for various structural parameters using finite-difference time-domain and COMSOL Multiphysics. The physical mechanisms behind the coupling and propagation of plasmons in this structure are explained in terms of the allowed modes in each section of the device.
    Journal of Applied Physics 12/2009; · 2.21 Impact Factor
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    ABSTRACT: We present an experimental demonstration of strong coupling between a surface plasmon propagating on a planar silver thin film and the lowest excited state of CdSe nanocrystals. Attenuated total reflection measurements demonstrate the formation of plasmon-exciton mixed states, characterized by a Rabi splitting of approximately 112 meV at room temperature. Such a coherent interaction has the potential for the development of nonlinear plasmonic devices, and furthermore, this system is akin to those studied in cavity quantum electrodynamics, thus offering the possibility to study the regime of strong light-matter coupling in semiconductor nanocrystals under easily accessible experimental conditions.
    Nano Letters 12/2009; 10(1):274-8. · 13.03 Impact Factor
  • T. J. Davis, K. C. Vernon, D. E. Gomez
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    ABSTRACT: In this paper, a plasmonic “ac Wheatstone bridge” circuit is proposed and theoretically modeled for the first time. The bridge circuit consists of three metallic nanoparticles, shaped as rectangular prisms, with two nanoparticles acting as parallel arms of a resonant circuit and the third bridging nanoparticle acting as an optical antenna providing an output signal. Polarized light excites localized surface plasmon resonances in the two arms of the circuit, which generate an optical signal dependent on the phase-sensitive excitations of surface plasmons in the antenna. The circuit is analyzed using a plasmonic coupling theory and numerical simulations. The analyses show that the plasmonic circuit is sensitive to phase shifts between the arms of the bridge and has the potential to detect the presence of single molecules.
    Journal of Applied Physics 09/2009; · 2.21 Impact Factor