Enhanced THz extinction of single plasmonic antennas with conically tapered waveguides

TL;DR

This paper demonstrates enhanced terahertz extinction of a single plasmonic bowtie antenna using a conically tapered waveguide, significantly increasing incident field intensity and suppressing background noise for improved spectroscopy.

Contribution

It introduces a novel experimental setup combining a conical waveguide with a plasmonic bowtie antenna to enhance THz field interaction and measurement sensitivity.

Findings

Field intensity at the antenna increased by a factor of 10.

Background radiation was effectively suppressed.

Potential for improved single-nanostructure THz spectroscopy.

Abstract

We demonstrate experimentally the resonant extinction of THz radiation by a single plasmonic bowtie antenna, formed by two n-doped Si monomers with a triangular shape and facing apexes. This demonstration is achieved by placing the antenna at the output aperture of a conically tapered waveguide, which enhances the intensity of the incident THz field at the antenna position by a factor 10. The waveguide also suppresses the background radiation that otherwise is transmitted without being scattered by the antenna. Bowtie antennas, supporting localized surface plasmon polaritons, are relevant due to their ability of resonantly enhancing the field intensity at the gap separating the two triangular elements. This gap has subwavelength dimensions, which allows the concentration of THz radiation beyond the diffraction limit. The combination of a bowtie plasmonic antenna and a conical waveguide may serve as a platform for far-field THz time-domain spectroscopy of single nanostructures placed in the gap.