Fig. 5: SHG and THG in vdW topological insulator metamaterials.
From: Second and third harmonic generation in topological insulator-based van der Waals metamaterials
a and b Schematic illustration of the single-SRR array embedding sample H1 (a) and H2 (b). c and d Emission spectra measured from the optically pumped samples c H1 and d H2, incorporating SSRR (black) and DSRR (red) design geometries, respectively. The spectra are measured in step-scan mode with a spectral resolution ~1 cm−1 and aperture size ~5 mm. The total light reflected by the samples was collected through the external input window of the FTIR spectrometer, with a silicon-bolometer connected to a lock-in amplifier for detection
