Fig. 3.

Generation of single-cycle Hermite–Gauss wavepacket. a Structure of nonlinear metasurface (NLMS) for generation of Hermite-Gauss(1,0) (HG₁₀) single-cycle terahertz beam. Arrows indicate the orientation of the split-ring resonators. Scanning electron microscope image of the center of the NLMS is shown in the enlarged picture. Scale bar is 1 μm. b Spatiotemporal profile of the single cycle HG₁₀ beam emitted from the NLMS in a. Spatial field profile along the dashed line is plotted in red. The ± signs mark the lobes of spatiotemporal quadrupole structure formed on the xz plane