Fig. 1. (a) Schematic of the experiment system. PM1–PM3 are off-axis PMs. The inset illustrates the geometry of the interaction between the laser and the water line. In subsequent experiments, the water line moves primarily along the x axis. (b) and (c) THz time-domain and frequency-domain amplitudes generated by 0.2 mm water line at x=−0.07mm and at α=0°.

Fig. 2. (a) THz peak electric field intensity as a function of x position with the water line diameter of 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm, respectively. (b)–(e) THz time-domain waveforms at the x positions with maximum peak amplitude in different diameter water lines.

Fig. 3. (a) Relative positional relationship between the water line and the laser induced plasma (including the two-dimensional dipole array diagram) during the movement of the water line. (b) Normalized THz peak electric field strength as a function of the x position for the water line of 0.2 mm; the experimental and simulation results are shown by dots and line.

Fig. 4. Experimental results of the angular distribution of THz energy produced by the water lines with three different diameters (0.2 mm, 0.3 mm, 0.4 mm) at the optimal x positions.