Fiber-Laser-Induced Cavitation: Transition from Plasma Formation to Bubble Nucleation

Despite extensive research on laser-induced cavitation bubble dynamics based on the given bubble nucleus assumption, the mechanism linking laser energy-induced optical breakdown to bubble nucleation dynamics remains poorly explored. In this Letter, we investigate the coupled dynamics of plasma and bubble formation induced by various laser energies using fiber lasers. Our findings show that the initial growth of the laser-induced bubble nucleus is driven by ionization-induced phase transitions, with plasma diffusion forming a pressure field that triggers secondary fluid expansion. We find that the oscillatory variations of the Weber number (We) and Mach number (Ma) span values from approximately 10⁻⁵ to 105 for We and from 10⁻⁶ to 10-1 for Ma, reflecting the wide range of dynamical regimes encountered across different stages in the laser-induced cavitation process. In addition, vortex ring formation is observed during the bubble evolution stage. The breakdown threshold and nucleation critical conditions are determined through parameterized energy, with the maximum of bubble radius Rb,max at low energies consistent with experimental results. This study offers a physical interpretation for optical breakdown nucleation dynamics and extends the quantitative application of laser-induced cavitation technology in diverse fluid fields.