The dynamics and distribution of debris on laser-ablated Ga-In-Sn liquid film

We experimentally and numerically investigated the hydrodynamics, fragmentation mechanisms, and debris distribution arising from the interaction of nanosecond laser pulses with a gallium-indium-tin (Ga-In-Sn) liquid film of micron-scale thickness. High-speed stroboscopic shadow photography was employed to visualize the splash crown and ejection of debris. The velocities of this debris, ranging from 329 to 4211 m s$^{-1}$, were found to scale with laser pulse energy ($E_p~=~0.9$-$36~\mathrm{mJ}$) and film thickness (h) according to $U~\propto~{E_p^{5/9}/h}$. This velocity was accurately described by a modified ablation and propulsion model. The numerical simulations provided insights into the underlying physics, including the expansion of high-pressure plasma zone, shock wave propagation, and the formation of significant negative pressure regions conducive to cavitation. Furthermore, the direction of minimal debris deposition is found to align with peak plasma luminous intensity, which is normal to the liquid film.