Abstract
Bare metal wires have recently been demonstrated as waveguides for transporting terahertz (THz) radiation, where the guiding mode is radially polarized surface Sommerfeld waves. In this study, we demonstrate high-efficiency coupling of a broadband radially polarized THz pulsed beam, which is generated with a polarization-controlled beam by a segmented half-wave-plate mode converter, to bare copper wires. A total coupling efficiency up to 16.8% is observed, and at 0.3 THz, the maximum coupling efficiency is 66.3%. The results of mode-overlap calculation and numerical simulation support the experimental data well.
Highlights
We have developed a new method to generate broadband and stable THz cylindrical vector beam [7], which is a promising candidate to realize efficient coupling to a metal wire [2]
Bare metal wires, which support a plasmonic mode, on their surfaces in THz range, are one of good candidates for THz waveguides with low loss and low dispersion [1]
To our knowledge, efficient coupling of broadband propagating THz wave to bare metal wires is not realized, and experimental investigations to determine coupling efficiency are not performed
Summary
We have developed a new method to generate broadband and stable THz cylindrical vector beam [7], which is a promising candidate to realize efficient coupling to a metal wire [2]. Most terahertz (THz) technologies rely on free propagation rather than waveguide transportation. Bare metal wires, which support a plasmonic mode, on their surfaces in THz range, are one of good candidates for THz waveguides with low loss and low dispersion [1]. Large mismatch between radially polarized mode in a metal wire waveguide and linearly polarized mode in a free space hampers efficient coupling.
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