We reveal for the first time by experiments that within a narrow parameter regime, two cavitation bubbles with identical energy generated in antiphase develop a supersonic jet. High-resolution numerical simulation shows a mechanism for jet amplification based on toroidal shock wave and bubble necking interaction. The microjet reaches velocities in excess of $1000\mathrm{m}{\mathrm{s}}^{-1}$. We demonstrate that potential flow theory established for Worthington jets accurately predicts the evolution of the bubble gas-liquid interfaces unifying compressible and incompressible jet amplification.

Herein, we investigated experimentally the dynamics of three laser-induced, same-sized, symmetrically aligned, and synchronized bubbles. Three synchronized laser beams split from the same beam using a Diffractive Optical Element splitter were focused on water, and then we obtained three bubbles. Another nanosecond laser pulse was used to probe the bubbles to obtain shadowgraphs. The exact delay of the excited and detected light was controlled using a delay generator. The results revealed that the maximum volumes of bubbles in arrays decrease as the normalized distance falls, while the lifetimes and translation increase. It was explained by the interaction between the acoustic radiation of bubbles and the surrounding bubbles. The shrinkage of linear bubble arrays exists an anomaly. The center bubbles were stretched, to ellipsoid, stick, even fractured, by the peripheral bubbles. The closer they are, the more distinct is the above phenomenon. However, when the normalized distance was sufficiently small, instead of being stretched, the center bubbles were compressed to disk shape and thus shrank with the whole array. Finally, the dependence of the distance on the energy transfer of the bubble system is also discussed.

The dynamics of a single cavitation bubble exposed to a transient acceleration is studied experimentally. A single cavitation bubble is seeded with a pulsed laser in a free-falling and impacting water-filled test tube. After impact, a pressure wave containing compression and rarefaction phases is generated and interacts with the bubble. The bubble dynamics is studied with high-speed imaging and compared to numerical simulations using the Keller–Miksis model. The timing of bubble seeding with respect to the pressure wave is varied, and a regime of enhanced collapse strength is found.

Revealing the expansion and interaction dynamics of multiple shock waves induced by a nanosecond laser is important for controlling laser surgery. However, the dynamic evolution of shock waves is a complex and ultrafast process, making it difficult to determine the specific laws. In this study, we conducted an experimental investigation into the formation, propagation, and interaction of underwater shock waves that are induced by nanosecond laser pulses. The effective energy carried by the shock wave is quantified by the Sedov-Taylor model fitting with experimental results. Numerical simulations with an analytic model using the distance between adjacent breakdown locations as input and effective energy as fit parameters provide insights into experimentally not accessible shock wave emission and parameters. A semi-empirical model is used to describe the pressure and temperature behind the shock wave taking into account the effective energy. The results of our analysis demonstrate that shock waves exhibit asymmetry in both their transverse and longitudinal velocity and pressure distributions. In addition, we compared the effect of the distance between adjacent excitation positions on the shock wave emission process. Furthermore, utilizing multi-point excitation offers a flexible approach to delve deeper into the physical mechanisms that cause optical tissue damage in nanosecond laser surgery, leading to a better comprehension of the subject.

The potential applications of laser-induced bubbles are gradually revealed. And the performance of multiple - bubbles also attracted considerable attention. This paper is intended to study the complex interaction among three in-line arranged in-phase bubbles. This work illustrates the interactions of three bubbles oscillation and the shockwave motion after the recombination of the plasma nanosecond laser excited. The Volume of Fluid (VOF) model is used to numerically analyze the behaviour of same equilibrium size, same distance and in-phase multiple-bubbles, which enables tracking of the gas-liquid interface and the field. The numerical results indicate that, in the expanding stage, due to the pressure gradient, bubbles at both ends move towards the centre, while the bubble surfaces facing to other bubbles get flattening. The central bubble has longer oscillation period than the side bubbles. In the shrinking stage, the side bubbles get deformation faster, and then collapse with a jet or get adhere to the central bubble. The initial high-pressure bubble radiates a shockwave at the beginning of the expansion. The shock wave propagates outwards from the point source in a circular pattern, resulting in interference in the overlap of the two shock waves. A curved pressure wave, which is parallel to the in-line array, is produced by the interference of multiple shock waves. The pressure wave decays to an acoustic wave after a certain distance according to its initial intensity. In particular, a significant variable γ=D/(R+R) deserves studying in this progress.