Dynamical Observation of Femtosecond-Laser-Induced Bubbles in Water Using a Single Laser Source for Probing and Sensing

Abstract

We report on dynamical observations of femtosecond-laser-generated bubbles in water using a single-laser-source pump/probe setup combined with stroboscopic imaging. With this simple setup, we accurately measure the transmission of a probe beam and simultaneously record images giving the size and lifetime of single-pulse-generated bubbles. Our experiments indicate that stable bubble nucleation can be obtained with pulses repetition rate up to 142 kHz, which offers promising perspectives for high-throughput jetting.

Cavitation dynamics and directional microbubble ejection induced by intense femtosecond laser pulses in liquids

“…This clearly indicates that the cavitation bubble overpressure is directly related to the energy deposited in the medium through ionization by the input laser pulse. This increase in bubble volume with input laser energy is also in agreement with other measurements in this sense [34,35].…”

Dynamics of tightly focused femtosecond laser pulses in water

“…Moreover, the trailing part of fs pulses was observed to support higher intensities during filamentation [38]. The CIB, due to fs pulses, were observed to live up to few tens of ns with energy-dependent sub-micron to micron diameters [5,37]. Though the CIB and their interaction is a hydrodynamic phenomenon lasting less than 1 ms which is relatively slow when compared to the ultrafast processes occurring later in the wake of the fs pulse, the laser-produced plasma starts expanding within 20 ps due to electron-ion energy transfer time, effectively inducing a temperature above 200 • C due to the ultrafast phase transitions [39].…”

“…The separation between the CIB at different points along the propagation direction decreased with increasing input power (figure 5(a)) and increasing NA ( figure 5(b)). We believe that the micron-sized CIB [5,37] along the propagation direction act like tiny spherical lenses for filament propagation by refocusing the diverging laser energy and the trailing edge of the pulse along the propagation axis overcoming the diffraction. This leads to increasing deposition of laser energy during the propagation of fs pulses and the enhanced SCE in the wake of fs pulses.…”

“…Beyond the threshold energy the CIB progresses as explosive vaporization due to phase explosion with peak focus temperatures >300 • C [5]. The phenomenon of CIB in water due to fs pulses is observed to start at intensities higher than TW cm −2 [36,40] and is strongly dependent on the pulse energy and duration and repetition rate [37]. The plasma shielding effect that counters the propagation of laser pulses inside the medium is observed to reduce as the incident pulse duration becomes shorter [36].…”