Terahertz Generation Enhanced by Nonlinear Filaments Interaction in Liquids

Enhanced terahertz (THz) radiation was observed in liquids via interaction of two noncollinear filaments of ultrashort pulses. As compared with THz generation driven by one filament, the observed enhancement was attributed to asymmetric plasma current due to filament-induced multiple frequency components in liquids. By tuning the relative polarization angles and pulse energies of the interacting filaments, we demonstrated that the interaction of the two filaments gave rise to plasma density modulation and high-intensity laser field in the intersection region, which resulted in blue-shifted supercontinuum generation. The newly generated blue frequency components enhanced asymmetric plasma current when it combined with the fundamental-wave filament at 800 nm, which led to stronger THz generation.