Understanding the physics of terahertz (THz) wave generation from water is essential for developing liquid THz sources. This letter reports detailed experimental measurements of THz wave emission by focusing intense laser pulses onto water films. The simulation based on a ponderomotive force-induced dipole is supported by the observation of the THz intensity dependence on the laser incidence angle. This work provides fundamental insights into the THz wave generation process in water and an alternative perspective for studying laser-induced breakdown in liquids.

The research done at the University of Rochester was sponsored by the Army Research Office under Grant No. W911NF-17-1-0428 and the Air Force Office of Scientific Research under Grant No. FA9550-18-1-0357); Tcypkin was supported by the Ministry of Education and Science of the Russian Federation (074-U01). This project was also carried out as a part of the State Assignment on Research Work for the University of Information Technology, Mechanics, and Optics at ITMO University in the Sphere of Scientific Activity.