Experimentally exploring the terahertz radiation in a long filament by a two-color laser field

We have experimentally investigated the propagation effect of terahertz (THz) radiation from a long filament by checking the evolution of THz temporal waveform through shifting the longitudinal position of a short filament. The results show that the relative delay and carrier-envelope phase of the THz waveform change linearly with the shifted distance of the filament. After measuring the longitudinal intensity distributions of laser fields in long filament, we reconstruct successfully the process of the polarization-controlled THz radiation in a long filament. Besides, we also discuss the efficiency and polarization of THz radiation from a long filament excited by a circularly polarized two-color laser field. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement