Fast dynamics and imaging of intense laser-driven liquid-confined copper plasma for controlled ablation and processing applications

The study of intense pulsed laser-induced plasma (LIP) is a fascinating area of research fostering a wide range of applications in nanoparticle synthesis, ablation physics, spectroscopy, and material processing. Here we demonstrate the hitherto unobserved nanosecond laser-driven plasma emission dynamics from a liquid-confined dense copper plasma over a time delay of a few nanoseconds to 10 s of nanoseconds, observation of the structural instability in the confined plasma, and the plasma emission spectra by imaging and spectroscopy. We further highlight the possible applications in biocompatible nanoparticle synthesis and controlled pulsed laser ablation for texturing. The target is excited using a focused pulsed laser (7 ns, 1064 nm) inside different liquids: deionized water, isopropanol, methanol, and dimethyl sulfoxide. Plasma emission has a decay time in the range of 2.6–5.8 ns when produced inside liquids compared to a long double exponential decay ($\sim$23 ns and $\sim$181 ns) in air. This highlights the fast temporal evolution of bremsstrahlung and radiative electron–ion recombination in the evolving dense, liquid-confined plasma. Optical imaging illustrates the structural evolution of the plasma in confined conditions. The splitting of plasma plumes is observed inside alcohol media. The copper nanocolloids produced by the repeated laser-solid interactions show plasmonic peaks in the visible range of UV–vis absorption spectra. The 3D surface profiles and optical images of the craters show enhanced control of the ablation process within liquids rather than in air. Methanol offers the best ablation efficiency and crater quality. Overall, our work will contribute to understanding complex LIP processes and greatly impact liquid-assisted laser-processing applications.