Limits...
Interaction mechanisms of cavitation bubbles induced by spatially and temporally separated fs-laser pulses.

Tinne N, Kaune B, Krüger A, Ripken T - PLoS ONE (2014)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laser Zentrum Hannover e.V., Biomedical Optics Department, Hannover, Germany.

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.

Show MeSH

Related in: MedlinePlus

Detailed bubble dynamics of two cavities in the observable interaction mechanism 7.The parameters to observe mechanism 7 were here a focus separation of Δr = 71.8 µm and a laser pulse energy of Epulse = 10.7-times Eth. The image series begins with the occurrence of the second cavity at 10 µs. Afterwards, the dominating jet formation in laser scanning direction is shown with the overall jet length by composing two images covering different imaging regions within the cuvette at the same time delay. A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S3 Figure).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4263672&req=5

pone-0114437-g004: Detailed bubble dynamics of two cavities in the observable interaction mechanism 7.The parameters to observe mechanism 7 were here a focus separation of Δr = 71.8 µm and a laser pulse energy of Epulse = 10.7-times Eth. The image series begins with the occurrence of the second cavity at 10 µs. Afterwards, the dominating jet formation in laser scanning direction is shown with the overall jet length by composing two images covering different imaging regions within the cuvette at the same time delay. A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S3 Figure).

Mentions: Inside water as sample medium, two temporally as well as spatially separated laser pulses showed a very complex interaction and hence different resulting bubble dynamics compared to the single bubble dynamics. For that reason the two-dimensional parameter space was analyzed regarding the various observable effects and mechanisms first. The different cavitation bubble dynamics are shown in Fig. 3 as series of 8 or more single pictures and, additionally, for mechanism 7 in Fig. 4. Here, starting at a time of 10.0 µs the depicted images are composed of two pictures taken at different imaging regions to cover the whole jet length. (A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S2 and S3 Figures). Depending on the scanning velocity, which defined the spatial focus separation Δr, and on the pulse energy comparatively to the breakdown threshold (encoding the temporal overlap) a number of characteristic interaction effects was detected (confer to dynamics in Fig. 3). In Fig. 5 a depiction is shown listing the ten different, overall observable interaction effects. The snapshots of characteristic interaction effects shown in Fig. 5 were selected from picture series of the whole oscillation dynamics.


Interaction mechanisms of cavitation bubbles induced by spatially and temporally separated fs-laser pulses.

Tinne N, Kaune B, Krüger A, Ripken T - PLoS ONE (2014)

Detailed bubble dynamics of two cavities in the observable interaction mechanism 7.The parameters to observe mechanism 7 were here a focus separation of Δr = 71.8 µm and a laser pulse energy of Epulse = 10.7-times Eth. The image series begins with the occurrence of the second cavity at 10 µs. Afterwards, the dominating jet formation in laser scanning direction is shown with the overall jet length by composing two images covering different imaging regions within the cuvette at the same time delay. A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S3 Figure).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263672&req=5

pone-0114437-g004: Detailed bubble dynamics of two cavities in the observable interaction mechanism 7.The parameters to observe mechanism 7 were here a focus separation of Δr = 71.8 µm and a laser pulse energy of Epulse = 10.7-times Eth. The image series begins with the occurrence of the second cavity at 10 µs. Afterwards, the dominating jet formation in laser scanning direction is shown with the overall jet length by composing two images covering different imaging regions within the cuvette at the same time delay. A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S3 Figure).
Mentions: Inside water as sample medium, two temporally as well as spatially separated laser pulses showed a very complex interaction and hence different resulting bubble dynamics compared to the single bubble dynamics. For that reason the two-dimensional parameter space was analyzed regarding the various observable effects and mechanisms first. The different cavitation bubble dynamics are shown in Fig. 3 as series of 8 or more single pictures and, additionally, for mechanism 7 in Fig. 4. Here, starting at a time of 10.0 µs the depicted images are composed of two pictures taken at different imaging regions to cover the whole jet length. (A more detailed time evolution of the effects and the whole dynamics in equidistant time steps is shown in the S2 and S3 Figures). Depending on the scanning velocity, which defined the spatial focus separation Δr, and on the pulse energy comparatively to the breakdown threshold (encoding the temporal overlap) a number of characteristic interaction effects was detected (confer to dynamics in Fig. 3). In Fig. 5 a depiction is shown listing the ten different, overall observable interaction effects. The snapshots of characteristic interaction effects shown in Fig. 5 were selected from picture series of the whole oscillation dynamics.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laser Zentrum Hannover e.V., Biomedical Optics Department, Hannover, Germany.

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.

Show MeSH
Related in: MedlinePlus