Theoretical and experimental studies of directivity of sound field generated by pulsed laser induced breakdown in liquid water

High power acoustic sources, generated by laser-induced breakdown when high power laser is focused into water, have extensive application prospects in laser medicine and ocean exploration. Combining the models of sound column and plasma disc in laser-induced breakdown generated sound field, a plasma cylinder model is established. The directivity of the sound field, and it’s characteristics are mapped and analyzed through numerical simulation, as well as theoretical analysis. An experiment is designed and performed to verify the plasma cylinder model. The experimental results, which are in a good agreement with the simulation, reveal the maximum pressure amplitude of the acoustic signals is at the direction vertical to the light propagation, and present a distinct major-lobe and minor-lobes.