Spectroscopy and mapping of resonant fields in terahertz plasmonic resonators

Abstract

Plasmonic terahertz (THz) resonators provide a promising route for exploring strong light-matter coupling phenomena. Double-metal resonator designs in particular enable strong enhancement of the THz field and provide well-defined field orientation and confinement within a sub-wavelength size volume. The strong field confinement however limits access to the internal fields essential for investigations of light-matter coupling. We propose and investigate a method for mapping and spectroscopic analysis of the internal fields in double-metal plasmonic THz resonators. We use aperture-type scanning near-field THz microscopy to access strongly confined fields with sub-wavelength spatial resolution of ~5 μm (~λ/100). Combined with the THz time-domain spectroscopy technique, the near-field method allows us to perform spectroscopic studies and investigate the field evolution inside the resonator. This experimental method opens doors to studies of strong light-matter coupling at THz frequencies in individual plasmonic resonators.