Dynamics of bubbles induced by multiple femtosecond laser pulses*

Femtosecond laser pulse interaction with transparent materials has captivated much attention in recent years. Nonlinear interaction of focused femtosecond laser pulses in liquids offer means for the micromachining of bulk materials and an accurate laser tool for photo disruptive surgery in tissues. Femtosecond laser-induced plasma in liquids results in filamentation and subsequent formation of bubbles. In the present work, high-speed imaging is used to reveal the Spatio-temporal evolution and interaction of these bubbles as a function of laser pulse energy (∼25 to 800 µJ), liquid medium (water, ethanol, and glycerol), and focusing optics (with and without spherical aberrations). The influence of the train of laser pulses of different energy on the filament length and size distribution of bubbles is discussed in detail. The introduction of multiple pulses leads to a strong interaction between the bubbles and controls the lifetime of the existing bubbles and the creation of new bubbles, thereby increasing the population and size of the bubbles. The incident laser energy and pulse width employed in this work can be advantageous in diverse industrial applications such as surface cleaning, microelectronics, and can be useful for medical procedures such as intraocular microsurgery.