Non-contact imaging of terahertz surface currents with aperture-type near-field microscopy

Terahertz (THz) near-field imaging and spectroscopy provide valuable insights into the fundamental physical processes occurring in THz resonators and metasurfaces on the subwavelength scale. However, so far, the mapping of THz surface currents has remained outside the scope of THz near-field techniq...

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Bibliographic Details
Published inOptics express Vol. 32; no. 14; p. 24200
Main Authors Norman, Sarah, Seddon, James, Lu, Yuezhen, Hale, Lucy, Zaman, Abdullah, Addamane, Sadhvikas J., Brener, Igal, Degl’Innocenti, Riccardo, Mitrofanov, Oleg
Format Journal Article
LanguageEnglish
Published 01.07.2024
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Summary:Terahertz (THz) near-field imaging and spectroscopy provide valuable insights into the fundamental physical processes occurring in THz resonators and metasurfaces on the subwavelength scale. However, so far, the mapping of THz surface currents has remained outside the scope of THz near-field techniques. In this study, we demonstrate that aperture-type scanning near-field microscopy enables non-contact imaging of THz surface currents in subwavelength resonators. Through extensive near-field mapping of an asymmetric D-split-ring THz resonator and full electromagnetic simulations of the resonator and the probe, we demonstrate the correlation between the measured near-field images and the THz surface currents. The observed current dynamics in the interval of several picoseconds reveal the interplay between several excited modes, including dark modes, whereas broadband THz near-field spectroscopy analysis enables the characterization of electromagnetic resonances defined by the resonator geometry.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.531690