Interaction Mechanisms of Cavitation Bubbles Induced by Spatially and Temporally Separated fs-Laser Pulses

Abstract

The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers.

Multi-pulse laser-induced bubble formation and nanoparticle aggregation using MoS2 nanoparticles

“…4. Factors such as the increase in pressure caused by the formation of the cavitation bubble 40,41 , changes in the optical force gradient 22 , and the surrounding medium can affect the bubble formation 42 . Differences in individual laser powers as well as the spatial and temporal overlap of the two pulses can change the profile of the force gradient of the optical trap and affect the heating of the bubble.…”

Sacrificial-layer free transfer of mammalian cells using near infrared femtosecond laser pulses

“…In addition, we use the near infrared window, where the interaction of radiation with biological material is minimal [ 21 , 22 ], thereby avoiding the risk of inducing photochemical DNA damage. In aqueous media, the high pressure plasma generated by the ultrashort laser pulses forms a rapidly expanding cavitation bubble [ 29 ]. When the femtosecond laser focus is placed to a focus depth of 50 μm to 100 μm underneath the liquid surface, the cavitation bubble can be used to propel a water or hydrogel jet, which is subsequently ejected from the free liquid surface [ 30 , 31 ].…”

Intraocular Pressure Study in Ex Vivo Pig Eyes by the Laser-Induced Cavitation Technique: Toward a Non-Contact Intraocular Pressure Sensor

“…These relations show that the first bubble collapse time τ c and its maximum bubble radius R max depend on the applied laser pulse energy [29]; part of this energy is converted into luminescence light, mechanical energy, i.e., shock waves, and about 20% of the laser pulse energy (for 6 ns pulses) is converted into bubble energy [28]. Therefore, based on Equation (4) and under constant bubble energy and media properties, it is possible to infer the liquid pressure by measuring the first bubble collapse time.…”