Rising dynamics of bubbles generated by femtosecond laser filamentation in water

Rising dynamics of bubbles generated by a femtosecond filament in water is monitored. Temporal evolution of the bubbles in the rising process is studied: the volume and rising velocity of the bubbles decrease. By increasing the incident pulse energy, the volume and rising velocity of the bubbles increase accordingly (lower than 200  μJ), while they stay nearly constant when further increasing the pulse energy (higher than 200  μJ), which can be attributed to the fact that the shape instability limits the size of the bubbles. The shape instability of bubbles leads to splitting of the bubbles: when the pulse energy is lower (1.6–26  μJ), the bubble may split into two smaller ones with comparable size; when the pulse energy is higher (26–600  μJ), a bigger bubble is generated, accompanied by smaller bubbles. The observed phenomena are analyzed via the relationship between femtosecond laser filamenation and evolution of bubbles. We hope this work can provide an approach to access the ultrafast plasma evolution in water through a long time evolution process (e.g., a rising process of bubbles).