ORCID Profile
0000-0003-3093-1618
Current Organisation
University of Technology Sydney
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Publisher: Elsevier BV
Date: 09-2016
Publisher: SPIE-Intl Soc Optical Eng
Date: 11-04-2018
Publisher: Wiley
Date: 11-2015
Abstract: A metamaterial absorber that effectively harvests solar energy is being proposed in this paper using a simple and high flexible structure. The proposed structure unit cell comprises of three vital layers. The ground metallic plane, an intermediate dielectric spacer while patches are wisely prepared on the top of a dielectric spacer. Geometrical parameters of the proposed metamaterial is studied in order to get insight on their impact for the absorption behaviour of the structure. The results from simulation provides two excellent absorption resonance (99.96% and 99.37%) in the visible spectrum range of electromagnetic wave. Due to the excellent symmetry of the proposed metamaterial design, its absorption coefficient is polarisation insensitive for a wide range of incident angles of electromagnetic radiations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Publisher: Optica Publishing Group
Date: 17-06-2022
DOI: 10.1364/OE.462117
Abstract: Nanosized particles with high responsivity in the infrared spectrum are of great interest for biomedical applications. We derive a closed-form expression for the polarizability of nanoparticles made of up to three concentric nanolayers consisting of a frequency dependent polar dielectric core, low permittivity dielectric spacer shell and conductive graphene outer shell, using the electrostatic Mie theory in combination with conductive layer in a dipole approximation. We use the obtained formula to investigate SiC, GaN and hBN as core materials, and graphene as conductive shell, separated by a low-permittivity dielectric spacer. Three-layer nanoparticles demonstrate up to a 12-fold increased mid-infrared (MIR) absorption as compared to their monolithic polar dielectrics, and up to 1.7 as compared to two-layer (no spacer) counterparts. They also show orders of magnitude enhancement of the nanoparticle scattering efficiency. The enhancement originates from the phonon-plasmon hybridization thanks to the graphene and polar dielectric combination, assisted by coupling via the low permittivity spacer, resulting in the splitting of the dielectric resonance into two modes. Those modes extend beyond the dielectric’s Reststrahlen band and can be tuned by tailoring the nanoparticles characteristics as they can be easily calculated through the closed-form expression. Nanoparticles with dual band resonances and enhanced absorption and scattering efficiencies in the MIR are of high technological interest for biomedical applications, such as surface -enhanced vibrational spectroscopies allowing simultaneous imaging and spectroscopy of s les, as well as assisting guided drug delivery.
Publisher: Elsevier BV
Date: 06-2016
Publisher: SPIE-Intl Soc Optical Eng
Date: 08-2017
Publisher: Springer Science and Business Media LLC
Date: 03-11-2016
Publisher: Elsevier BV
Date: 10-2015
Publisher: IOP Publishing
Date: 07-2020
Abstract: The ability to control the interaction of light and matter at the nanoscale is at the heart of the field of nanophotonics. This subdiffractional confinement of light can be achieved through the stimulation of surface polaritons, most notably surface plasmon polaritons (SPPs). However, the high optical losses and lack of tunability of conventional plasmonic materials have hindered major progress in this field. In the search for alternative low-loss and tunable materials, graphene and polar dielectric materials are viewed as potential alternatives to more common metal-based plasmonic materials. In particular, the possibility of combining the tunable nature of graphene SPPs with the high-quality factors and long lifetimes of surface phonon-polaritons (SPhPs) modes supported in polar dielectric materials (e.g. SiC) offers great promise for advanced nanophotonic applications. The combination of graphene SPPs and SPhPs supported in SiC is even more pertinent as this material system can be realized in the form of epitaxial graphene (EG), whereby sublimation of silicon from a SiC results in a surface reconstruction into a graphene surface termination. This offers an ideal technology platform for realizing hybrid SPP-SPhP modes. In this review, we outline advances in graphene plasmonics and the generation of SPhPs in polar materials, in the context of epitaxial graphene. We review recent attempts at realizing such coupling of graphene SPPs with phonon and SPhP modes in SiC, as well as covering such modes in other polar materials and conclude with an overview of advantages and challenges for further advancement of nanophotonics based on graphene on silicon carbide for on-chip light manipulation.
Publisher: Institution of Engineering and Technology (IET)
Date: 12-2016
Publisher: Optica Publishing Group
Date: 2020
DOI: 10.1364/CLEOPR.2020.C11E_2
Abstract: The mid-infrared optical spectrum hosts a variety of promising photonic applications. Herein we simulate and experimentally demonstrate reflectance enhancement of MIR light using graphene-coated silicon carbide nanowires on silicon, showing promise for on-chip MIR nanophotonics.
Publisher: MDPI AG
Date: 08-09-2021
DOI: 10.3390/NANO11092339
Abstract: The mid-infrared (MIR) is an exciting spectral range that also hosts useful molecular vibrational fingerprints. There is a growing interest in nanophotonics operating in this spectral range, and recent advances in plasmonic research are aimed at enhancing MIR infrared nanophotonics. In particular, the design of hybrid plasmonic metasurfaces has emerged as a promising route to realize novel MIR applications. Here we demonstrate a hybrid nanostructure combining graphene and silicon carbide to extend the spectral phonon response of silicon carbide and enable absorption and field enhancement of the MIR photon via the excitation and hybridization of surface plasmon polaritons and surface phonon polaritons. We combine experimental methods and finite element simulations to demonstrate enhanced absorption of MIR photons and the broadening of the spectral resonance of graphene-coated silicon carbide nanowires. We also indicate subwavelength confinement of the MIR photons within a thin oxide layer a few nanometers thick, sandwiched between the graphene and silicon carbide. This intermediate shell layer is characteristically obtained using our graphitization approach and acts as a coupling medium between the core and outer shell of the nanowires.
Location: Rwanda
No related grants have been discovered for Patrick Rufangura.