s-SNOM imaging of a THz photonic mode

We report on the imaging by THz s-SNOM of the field concentration associated to the photonic mode of a split-ring resonator with a 2 μm small gap. The ability to concentrate and probe THz radiations at this scale is of interest for studies on micro and nano objects. Our results are interpreted with numerical calculations as an interplay between the confined near-field and the directional far-field emission of the system.