Paper
8 June 2011 Interaction dynamics of fs-laser induced cavitation bubbles and their impact on the laser-tissue-interaction of modern ophthalmic laser systems
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Abstract
A today well-known laser based treatment in ophthalmology is the LASIK procedure which nowadays includes cutting of the corneal tissue with ultra-short laser pulses. Instead of disposing a microkeratome for cutting a corneal flap, a focused ultra-short laser pulse is scanned below the surface of biological tissue causing the effect of an optical breakdown and hence obtaining a dissection. Inside the tissue, the energy of the laser pulses is absorbed by non-linear processes; as a result a cavitation bubble expands and ruptures the tissue. Hence, positioning of several optical breakdowns side by side generates an incision. Due to a reduction of the amount of laser energy, with a moderate duration of treatment at the same time, the current development of ultra-short pulse laser systems points to higher repetition rates in the range of even Megahertz instead of tens or hundreds of Kilohertz. In turn, this results in a pulse overlap and therefor a probable occurrence of interaction between different optical breakdowns and respectively cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. Thus, the aim of this study is to analyse the dynamic and interaction of two cavitation bubbles by using high speed photography. The applied laser pulse energy, the energy ratio and the spot distance between different cavitation bubbles were varied. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape or jet formation are observed. The effects will be discussed regarding the medical ophthalmic application of fs-lasers. Based on these results a further research seems to be inevitable to comprehend and optimize the cutting effect of ultra-short pulse laser systems with high (> 500 kHz) repetition rates.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
N. Tinne, T. Ripken, H. Lubatschowski, and A. Heisterkamp "Interaction dynamics of fs-laser induced cavitation bubbles and their impact on the laser-tissue-interaction of modern ophthalmic laser systems", Proc. SPIE 8092, Medical Laser Applications and Laser-Tissue Interactions V, 80921H (8 June 2011); https://doi.org/10.1117/12.889341
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KEYWORDS
Cavitation

Laser tissue interaction

Laser vision correction

Laser cutting

Pulsed laser operation

Laser energy

Tissue optics

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