Role of Liquid Water in Terahertz Radiation and Application

Terahertz (THz) generation and detection using liquid water has long been considered impossible due to its strong absorption of THz wave. A few very recent works reported THz generation from water, but the mechanism has not yet been well clarified and the efficiency demands to be further enhanced. In general, the THz generation and detection are considered as "reversible" theoretical analysis processes. We explore the potential of liquid water as efficient scheme of table-top THz generator and detector. Further underlying physical mechanism, such as the ultrafast electron migration and solvation need to be considered. Moreover, the complex low-frequency molecular motion of water in the THz range has also been successfully identified by the THz Kerr effect technique on the sub-picosecond time scale.