Broadband THz Wave Generation from Flowing Liquid Nitrogen

We successfully demonstrate broadband THz wave emission from cryogenic fluid - liquid nitrogen - by focusing laser pulses on a flowing liquid nitrogen line in the ambient environment. The THz signal from liquid nitrogen shows a comparable field strength with a broader bandwidth to that from liquid water. In contract to solid materials or other liquids, liquid nitrogen is a “debris-free” target, which can sustain the excitation with high repetition rate laser pulses. This work provides more possibilities in studying laser-induced ionization of cryogenic liquids.