Kristy Vernon

Queensland University of Technology | QUT · School of Chemistry, Physics and Mechanical Engineering

In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 × 10(-4) RIU (refractive index uni...

Vertical graphene nanosheets have advantages over their horizontal counterparts, primarily due to the larger surface area available in the vertical systems. Vertical sheets can accommodate more functional particles, and, due to the conduction and optical properties of thin graphene, these structures can find niche applications in the development of...

Light trapping, due to the embedding of metallic nanoparticles, has been shown to be beneficial for a better photoabsorption in organic solar cells. Researchers in plasmonics and in the organic photovoltaics fields are working together to improve the absorption of sunlight and the photon–electron coupling to boost the performance of the devices. Re...

Gold particle interaction with few-layer graphenes is of interest for the development of numerous optical nanodevices. The results of numerical studies of the coupling of gold nanoparticles with few-layer vertical graphene sheets are presented. The field strengths are computed and the optimum nanoparticle configurations for the formation of surface...

In this paper, we modeled a quantum dot at near proximity to a gap plasmon waveguide to study the quantum dot-plasmon interactions. Assuming that the waveguide is single mode, this paper is concerned about the dependence of spontaneous emission rate of the quantum dot on waveguide dimensions such as width and height. We compare coupling efficiency...

Active control of plasmon propagation via coupling to Quantum Dots (QDs) is a hot topic in nano-photonic research. When a QD is excited it acts like a dipole emitter. If this excited QD is placed near a metallic waveguide structure, it can decay either radiatively into bulk electromagnetic radiation, non-radiatively into heating of the metal or, of...

Active control of plasmon propagation via coupling to Quantum Dots (QDs) is a hot topic in nano-photonic research. When a QD is excited it acts like a dipole emitter. If this excited QD is placed near a metallic waveguide structure, it can decay either radiatively into bulk electromagnetic radiation, non-radiatively into heating of the metal or, of...

The interaction of Au particles with few layer graphene is of interest for the formation of the next generation of sensing devices 1. In this paper we investigate the coupling of single gold nanoparticles to a graphene sheet, and multiple gold nanoparticles with a graphene sheet using COMSOL Multiphysics. By using these simulations we are able to d...

The properties of ellipsoidal nanowires are yet to be examined. They have likely applications in sensing, solar cells, microelectronics and cloaking devices. Little is known of the qualities that ellipse nanowires exhibit as we vary the aspect ratio with different dielectric materials and how varying these attributes affects plasmon coupling and pr...

Fabrication of one-dimensional arrays of crystalline nanoparticles with tunable particle size and spacing (down to 20 nm) is demonstrated. The individual nanocrystals are pentagonal prisms, and the arrays are up to 11 μm in length, with some arrays containing >50 nanocrystals. Precise particle morphology and interparticle spacing can be maintained...

The field of plasmonics has emerged with promising applications in novel scientific areas of research such as plasmonic solar cells and integrated photonic circuits.1 For most photonic circuitry, light should be confined and routed into a volume far beneath the diffraction limit. One solution is the plasmonic waveguide. There are several configurat...

A seven-year study has been conducted on female enrolment in physics, from bachelors through to PhD, at QUT. An overall increase in female participation, with the highest percentage increase in research degree has been reported.

We present experimental results that demonstrate that the wavelength of the fundamental localized surface plasmon resonance for spherical gold nanoparticles on glass can be predicted using a simple one-line analytical formula derived from the electrostatic eigenmode method. This allows the role of the substrate in lifting mode degeneracies to be de...

We derive a semianalytical model to describe the interaction of a single photon emitter and a collection of arbitrarily shaped metal nanoparticles. The theory treats the metal nanoparticles classically within the electrostatic eigenmode method, wherein the surface plasmon resonances of collections of nanoparticles are represented by the hybridizati...

This work is a theoretical investigation into the coupling of a single excited quantum emitter to the plasmon mode of a V groove waveguide. The V groove waveguide consists of a triangular channel milled in gold and the emitter is modeled as a dipole emitter, and could represent a quantum dot, nitrogen vacancy in diamond, or similar. In this work th...

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...

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 stri...

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 particul...

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 particul...

We study the coupling of emitters such as quantum dots to plasmonic waveguides consisting of a triangular channel milled into metal. In particular, the effect of varying groove angle, tip radius, groove depth, and emitter position on the coupling efficiency is investigated. The finite element method is employed in two-and three dimensional simulati...

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. I...

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 ar...

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. Bec...

We present a theory for determining the localized surface plasmon resonance shifts of arbitrarily shaped metal nanoparticles on a substrate. Using a pseudoparticle concept, an expression for the particle-substrate interaction is derived, providing both physical insight and formulas to estimate the shifted plasmon resonance. The theory is verified a...

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 en...

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 ens...

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 eigenfunct...

The localized surface plasmon resonances in a metallic nanorod are determined using the "electrostatic approximation" and by a finite-difference time-domain numerical solution of Maxwell's equations. The difference between the two methods is related to the effects of re-radiation, or retardation, which is not included in the electrostatic formulati...

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...

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 tempe...

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...

The design of structures capable of producing strong electric near-fields has become an active area of plasmonics research with applications including sensor technology, surface enhanced Raman scattering and plasmon solar cells. The purposeful design of plasmonic systems is complicated by the problem of finding analytical solutions to Maxwell's equ...

The propagation of surface plasmons in thin films is important for a number of technologies and has found applications in chemical and biological sensing. There is growing interest in the use of surface plasmons coupled with optical systems for high density photonic devices. While the analysis of the properties of surface plasmons at a metal-dielec...

A theory of the coupling of evanescent optical fields between metallic nanoparticles is developed to provide a basis for designing plasmonic systems. The interaction between metallic nanoparticles is investigated using an electrostatic approximation that describes the localized surface-plasmon resonances for particles much smaller than the waveleng...

We investigated the effect of dielectric filling in a V groove on the propagation parameters of channel plasmon-polariton (CPP) modes. In particular, existence conditions and critical groove angles, mode localization, field structure, dispersion, and propagation distances of CPP modes are analyzed as functions of dielectric permittivity inside the...

Here, we demonstrate that efficient nano-optical couplers can be developed using closely spaced gap plasmon waveguides in the form of two parallel nano-sized rectangular slots in a thin metal film or membrane. Using the rigorous numerical finite-difference and finite element algorithms, we investigate the physical mechanisms of coupling between two...

We demonstrate that efficient adiabatic nanofocusing of plasmons can be achieved using a sharp metal wedge (thin tapered film) on a dielectric substrate. It is shown that the quasi-symmetric (with respect to the charge distribution across the wedge) plasmon mode can experience infinite adiabatic slowing down with both its phase and group velocities...

In this paper, we demonstrate the possibility of efficient adiabatic nano-focusing of plasmons by a sharp triangular metal wedge. The geometrical optics approach and the approximation of continuous electrodynamics are used for the analysis. In particular, it is demonstrated that both the phase and group velocities of an incident anti-symmetric (wit...

We report numerical analysis and experimental observation of two-dimensionally localized plasmonic modes guided by a nano-gap in a thin metal film. Dispersion, dissipation and field structure of these modes are analyzed using the finite-difference time-domain algorithm. The experimental observation is conducted by the end-fire excitation of the pro...

Strongly localised plasmons in metallic nano-structures offer exciting characteristics for guiding and focusing light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved resolution of optical microscopy. The work presented in this thesis focuses on two major areas of plasmonics research - nano-focu...