Observation of Strong Terahertz Radiation from a Liquid Water Line

Abstract

Terahertz radiation generation from liquid water has long been considered to be impossible due to strong absorption. A few very recent works reported terahertz generation from water, but the mechanism is not clear and the efficiency demands to be enhanced. We show experimentally that strong single-cycle terahertz radiation with field strength of $0.2\mathrm{MVc}{\mathrm{m}}^{-1}$ is generated from a water line/column of $\sim 200\mu m$ in diameter irradiated by a mJ femtosecond laser beam. This strength is 100-fold higher than that produced from air. We attribute the mechanism to the laser-ponderomotive-force-induced current with the symmetry broken around the water-column interface. This mechanism can explain our following observations: the radiation can be generated only when the laser propagation axis deviates from the column center; the deviation determines its field strength and polarity; it is always p-polarized no matter whether the laser is p- or s-polarized. This study provides a simple and efficient scheme of table-top terahertz sources based on liquid water.

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References in corpus (2)

• Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios
• Integrated simulation approach for laser-driven fast ignition