Figure 4. Time-averaged current norm distributions on the 55-μm-height spiral for right and left circularly polarized light (denoted as RCP and LCP, respectively).

(a–c) Correspond to the distributions at the frequency of 0.45, 0.67 and 1.08 THz, respectively. The corresponding frequencies are indicated by markers in Fig. 3h as α, β and γ, respectively. A bar in a indicates 50 μm. The arrows in these distribution figures indicate the current direction at a certain time: red and blue arrows correspond to the clockwise (CW) and anti-clockwise (ACW) current directions seen from the −z direction to +z direction.