Observation of Broadband Terahertz Wave Generation from Liquid Water

Abstract

Liquid water is a strong absorber in THz range, making the presence of water a nuisance when collecting measurements within this frequency regime. Here, we experimentally demonstrate the generation of broadband THz waves from liquid water with a femtosecond laser. The signal is obtained when a high-intensity laser beam is focused within a water film. This THz signal is distinguished from the signal generated with air plasma by translating the water film across the focal spot. Our observation demonstrates the possibility that liquid water can be a competitive THz source. Our research is also expected to enrich the study of laser-water interactions.