In this study a single laser pulse spatially shaped into a ring is focused into a thin water layer, creating an annular cavitation bubble and cylindrical shock waves: an outer shock that diverges away from the excitation laser ring and an inner shock that focuses towards the center. A few nanoseconds after the converging shock reaches the focus and diverges away from the center, a single bubble nucleates at the center. The inner diverging shock then reaches the surface of the annular laser-induced bubble and reflects at the boundary, initiating nucleation of a tertiary bubble cloud. In the present experiments, we have performed time-resolved imaging of shock propagation and bubble wall motion. Our experimental observations of single-bubble cavitation and collapse and appearance of ring-shaped bubble clouds are consistent with our numerical simulations that solve a one-dimensional Euler equation in cylindrical coordinates. The numerical results agree qualitatively with the experimental observations of the appearance and growth of large bubble clouds at the smallest laser excitation rings. Our technique of shock-driven bubble cavitation opens interesting perspectives for the investigation of shock-induced single-bubble or multibubble cavitation phenomena in thin liquids.

Two pairs of converging and superimposing shock and Rayleigh waves are generated on a glass substrate by focusing laser pulses on two concentric rings in a bullseye configuration (67 and 96  μm radii). We experimentally study the threshold for the substrate damage as a function of the number of repetitions and the delay (0–20 ns). The bullseye focusing experiments are compared to a single focusing ring. Additionally, fluid–structure interaction simulations using a volume-of-fluid framework are utilized to estimate the stresses. The lowest number of repetitions to attain surface damage is found for constructive superposition of the Rayleigh waves, i.e., here for a delay of 10 ns. The observed damage is consistent with the simulations where the largest positive stresses ([Formula: see text] GPa) are achieved for bullseye focusing with [Formula: see text] ns followed by [Formula: see text] ns, which corresponds to a simultaneous shock wave focusing. In all these cases, the positive stresses are followed (a few nanoseconds later) by the negative stresses that can reach [Formula: see text] GPa.

Abstract

A method is presented to carve into a glass submerged in water with laser‐induced surface and shock waves. It starts with an elliptic wave source that launches an elliptically converging Rayleigh and shock wave. At the wave focus a single microscopic crack with controlled location and orientation is induced that has a length of a few micrometers and a width of about 100 nm. Through successive surface waves, this crack may be extended along a specific direction which can be controlled by adjusting the distance, shape, and orientation of the laser focus. Here, either point‐like or elliptical laser foci are generated using a spatial light modulator. Furthermore, when the crack is guided along a closed circular path using a point like laser focus, a conchoidal hole may be carved through the glass slide demonstrated with a 160 µm thick cover slip. The shock waves are modeled in the fluid and the elastic waves in the glass in three dimensions with a finite‐volume framework that accounts for fluid‐structure interaction. The resulting pressures and stresses for both the elliptical and point‐like Rayleigh and shock wave sources are reported.