Abstract-Enhancement of terahertz emission by a preformed plasma in liquid water

Applied Physics Letters

Yiwen E, Qi Jin, X.-C. Zhang,

Experimental setup. (a) Two collinearly propagating main- and prepump beams are focused by a lens to ionize a water line (top view). The time delay (Δτ) between two optical pumps is controlled by a translation stage. The THz signal is detected through electro-optical sampling (EOS) in the forward direction. Additionally, the pulse duration is monitored by an optical autocorrelator. (b) A photo of a 210 μm water line (side view).

https://aip.scitation.org/doi/abs/10.1063/1.5119812

Terahertz (THz) wave generation from liquids under optical excitation has been experimentally confirmed. Here, we report the observation of THz emission enhancement from liquid water with a preformed plasma. Two collinear optical beams with a controlled time delay are focused into a liquid water line. With a plasma created by the first optical pump, the THz emission generated by the second pump is enhanced significantly. By using the same total incident energy compared to the commonly used single-pump excitation, an enhancement over 8 times is observed when the prepump is s-polarized. This observation provides an alternative strategy to boost THz generation from liquids and helps to further understand the laser-liquid interaction process.

The research at the University of Rochester was sponsored by the Army Research Office under Grant No. W911NF-17-1-0428, Air Force Office of Scientific Research under Grant No. FA9550-18-1-0357, and National Science Foundation under Grant No. ECCS-1916068.