Exploring liquid plasma jets using short laser pulses

Laser-induced plasmas play an important role in many applications. They can be used as versatile radiation sources, and they are invaluable in spectroscopy. However, most research in this field focuses on plasmas from either solid or gaseous sources, while laser-induced liquid plasmas are less well understood.

To address this knowledge gap, Ponomareva et al. developed a method to produce a detailed analysis of the optical behavior of laser-induced liquid plasmas. The researchers measured the reflections of a subpicosecond laser pulse to uncover both static and time-dependent properties of the plasma.

“We show what are the optical properties of plasma induced via the optical breakdown in liquid jets and compare them for water and ethanol,” said author Anton Tcypkin. “Our research opens up a new method for analyzing the generated laser-induced plasma.”

The researchers performed a single-pulse experiment to measure the relationship between pump energy and incident angle on the plasma’s reflectivity and a time-resolved double-pulse experiment to measure the reflected energy as a function of the delay between the pulses.

In the single-pulse experiment, the researchers found a strong correlation between the reflectivity of the plasma and the pump energy and pump angle in the static regime.

The double-pulse experiment sought to uncover dynamic behaviors using samples of both water and ethanol. The researchers discovered particularly interesting behaviors from the ethanol, including a change in the reflected energy that scales linearly with the duration of the initial pulse.

The researchers next plan to explore these dynamic effects with other liquids and possibly pressurized gases over a wider range of frequencies.

Source: “Plasma reflectivity behavior under strong subpicosecond excitation of liquids,” by E. Ponomareva, A. Ismagilov, S. Putilin, and A. Tcypkin, APL Photonics (2021). The article can be accessed at https://doi.org/10.1063/5.0070963 .