Terahertz wave emission from plasmonic chiral metasurfaces

Plasmonic chiral metasurfaces with pinwheel-like structures are fabricated on silver films using a focused ion-beam milling technique. In time-domain spectroscopy, we observe terahertz (THz) wave emission from metasurfaces irradiated by a near-infrared Ti:sapphire ultrashort pulsed laser. The origin of the THz wave generation is likely to be tunnelling ionization accompanied with photoelectron acceleration by ponderomotive force. Numerical simulation is carried out toward improvement of the chiral metasurfaces for better emission of circularly polarized THz waves.