Fig. 1.

Metasurface characteristics. a Structure of the split-ring resonators (SRRs) that were used as basic inclusion for the nonlinear metasurface (NLMS). b Scanning electron microscope image of the fabricated SRRs. Scale bar is 200 nm. c Transmission plot for horizontal and vertical polarizations (relative to the SRR orientation in a), showing a dip in the transmission around 1500 nm in the horizontal polarization, associated with the magnetic resonance of the SRR. d Illustration of excited linear and nonlinear currents in SRR. Excitation with near infrared (NIR) pulse (blue) polarized along the x axis excites surface currents along the SRR. As a result, nonlinear currents (green) are generated along the arms of the SRR, in the y axis direction