Periodic phase shifts of longitudinally resolved terahertz radiation along two-color filament in air

Abstract

The evolution of THz waveform generated from the two-color air filament was experimentally investigated by moving an iris along the plasma channel. By taking the differentiation of the measured THz waveforms, the longitudinally resolved THz waves along 54 mm long filament were obtained. The local THz pulse undergoes periodic phase shifts. Theoretical deduction indicates that the phase shifts are mainly caused by the dispersion in the plasma channel which plays a dominant role in the evolution of the local THz waveforms.