THz generation from liquid metal . (a) Schematic of the experimental setup. A two-dimensional translation stage is used to control the position of the -axis and the -axis of the liquid metal line. The optical beam propagates along the -axis. THz emission is measured by a standard electro-optical sampling. (b) Comparison of THz waveforms generated from air, water, and liquid gallium under single-color excitation. The target diameter is 210 μm. The THz signal from air plasma is enlarged by 10 times. (c) Normalized THz field strength plotted as a function of the -axis position. The dashed lines represent the -axis position of the maximum THz fields. The gray area shows the diameter of the liquid line.