Plasma Characterization in Liquid Jets through Third Harmonic Reflection

The double pump technique was employed to conduct time-resolved experiment on the third harmonic (TH) reflection dynamics from femtosecond laser-induced plasma in three distinct liquid jets (water, ethanol, isopropyl). By analyzing the TH reflection dynamics, we elucidated the plasma behavior at different time delays (ranging from 0 to 10 ps) between the double pump pulses. Plasma degradation time was determined in each liquid jet, with faster degradation observed in ethanol and isopropyl compared to water. Additionally, the plasma frequency as a function of the time delay between the double pump pulses was estimated in each liquid. These findings were validated through a theoretical model based on Keldysh theory.