Last piece of puzzle: THz wave emission from liquid water

Abstract

Liquid water is a strong absorber in the THz frequency range, meaning that liquid water has historically been sworn off as a source for THz radiation. Here, we experimentally demonstrate the generation of broadband THz waves from liquid water excited by femtosecond laser pulses. The THz radiation from liquid water shows distinct characteristics when compared with the THz radiation from air plasma with single color optical excitation. In contrast to THz air photonics, wherein a short optical pulse duration results in a stronger THz field due to nonlinear optical effects, the THz field from liquid water is eminently maximized with a longer laser pulse duration. Here, I will present our recent experimental demonstration [1] and postulate the physical model responsible for this generation.