Non-Invasive Near-field Spectroscopy of Single Sub-Wavelength Complementary Resonators

Abstract

Subwavelength metallic resonators provide a route to achieving strong light-matter coupling by means of tight confinement of resonant electromagnetic fields. Investigation of such resonators however often presents experimental difficulties, particularly at terahertz (THz) frequencies. A single subwavelength resonator weakly interacts with THz beams, making it difficult to probe it using far-field methods; whereas arrays of resonators exhibit inter-resonator coupling, which affects the resonator spectral signature and field confinement. Here, traditional far-field THz spectroscopy is systematically compared with aperture-type THz near-field microscopy for investigating complementary THz resonators. Whilst the far-field method proves impractical for measuring single resonators, the near-field technique gives high signal-to-noise spectral information, only achievable in the far-field with resonator arrays. At the same time, the near-field technique allows us to analyze single resonators - free from inter-resonator coupling present in arrays - without significant interaction with the near-filed probe. Furthermore, the near-field technique allows highly confined fields and surface waves to be mapped in space and time. This information gives invaluable insight into resonator spectral response in arrays. This near-field microscopy and spectroscopy method enables investigations of strong light-matter coupling at THz frequencies in the single-resonator regime.

arXiv comment29 pages, 8 figures

References in corpus (9)

• Ultrastrong coupling of the cyclotron transition of a two-dimensional electron gas to a THz metamaterial
• Light-matter decoupling in the deep strong coupling regime: The breakdown of the Purcell effect
• Ultrastrong Coupling in the Near-field of Complementary Split Ring Resonators
• Spontaneous Conversion from Virtual to Real Photons in the Ultrastrong Coupling Regime
• Nonclassical Radiation from Thermal Cavities in the Ultrastrong Coupling Regime
• Strong influence of packing density in terahertz metamaterials
• Ultra-Strong Light-Matter Coupling in Deeply Subwavelength THz LC resonators
• Direct characterization of near-field coupling in gap plasmon-based metasurfaces
• Superradiantly limited linewidth in complementary THz metamaterials on Si-membranes

Cited by in corpus (1)

• An ultrastrongly coupled single THz meta-atom