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18 January 1995 Laser surgery at the micrometer scale: possibilities and limitations
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Proceedings Volume 2323, Laser Interaction with Hard and Soft Tissue II; (1995)
Event: International Symposium on Biomedical Optics Europe '94, 1994, Lille, France
For a few years promising techniques have been worked out for microsurgery of cells and organelles by laser micro-cutting and micro-drilling. In this paper the specific requirements for controlled and safe laser surgery at this scale are addressed. Laser micro-drilling is investigated for various interaction parameters. For this a Nd:YAG laser ((lambda) equals 1064 nm) in Q-switched (7 ns) mode and a cw diode laser ((lambda) equals 1.48 micrometers ) in pulsed mode are used. The lasers are coupled to an inverted microscope and focused through the microscope objective (40X and 45X) in a spot of 1 to 3 micrometers in diameter. Ablation of biological targets (mouse zygotes zona pellucida) is compared with ablation of model targets (ink films), all in liquid environment. Possible generation of acoustical transients and cavitation bubbles is monitored with a PVDF pressure transducer and by time resolved video flash photography. The results show that, for the pulse durations investigated, a large absorption coefficient is a necessary condition for controlled micro-drilling. In liquid environment, short pulse lasers in combination with a low light absorption coefficient of the target induce unacceptable mechanical effects related to the generation of a cavitation bubble. These effects are due to a too high energy threshold for ablation in these processes. Video images of the drilled holes reveal walls of regular shape with small surrounding damage immediately after laser irradiation, which are completely destroyed at the bubble collapse. By contrast, with the 1.48 micrometers laser diode, which is strongly absorbed by the target, reproducible micro-drillings without mechanical effects are performed.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Klaus Rink, Guy P. Delacretaz, Rene-Paul Salathe, Alfred Senn, Dorotha Nocera, and Marc Germond "Laser surgery at the micrometer scale: possibilities and limitations", Proc. SPIE 2323, Laser Interaction with Hard and Soft Tissue II, (18 January 1995);


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