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Terahertz Localized Surface Plasmon Resonances in Coaxial Microcavities

Authors

  • Withawat Withayachumnankul,

    Corresponding author
    1. Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria, Australia
    • School of Electrical & Electronic Engineering, The University of Adelaide, Adelaide, South Australia, Australia
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  • Charan Manish Shah,

    1. Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria, Australia
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  • Christophe Fumeaux,

    1. School of Electrical & Electronic Engineering, The University of Adelaide, Adelaide, South Australia, Australia
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  • Korbinian Kaltenecker,

    1. Department of Molecular and Optical Physics, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
    2. French-German Research Institute Saint-Louis, Saint-Louis Cedex, France
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  • Markus Walther,

    1. Department of Molecular and Optical Physics, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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  • Bernd M. Fischer,

    1. School of Electrical & Electronic Engineering, The University of Adelaide, Adelaide, South Australia, Australia
    2. French-German Research Institute Saint-Louis, Saint-Louis Cedex, France
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  • Derek Abbott,

    1. School of Electrical & Electronic Engineering, The University of Adelaide, Adelaide, South Australia, Australia
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  • Madhu Bhaskaran,

    1. Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria, Australia
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  • Sharath Sriram

    Corresponding author
    • Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria, Australia
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E-mail: withawat@eleceng.adelaide.edu.au, sharath.sriram@gmail.com

Abstract

Coaxial microcavities etched into the surface of a doped silicon substrate are shown to support localized surface plasmon resonances at terahertz frequencies. The underlying mechanism involves coupling freely propagating terahertz waves with surface plasmon polaritons (SPPs), which propagate in a coaxial mode along the cavity walls in the axial direction. A Fabry–Pérot resonance is built up when the SPP wavenumber appropriately relates to the cavity depth. Owing to the Ohmic loss of the silicon at terahertz frequencies, the energy of the resonating SPPs is largely dissipated, leading to a modified reflection spectrum. Strong field enhancement is observed inside the cavities at resonance. The theoretical analysis is supported by numerical and experimental results. This study is a promising pathway for development of terahertz devices with applications in the areas of photonic integrated circuits, molecular sensing, and subwavelength imaging.

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