27 August 2003 Laser-tissue interaction with fs pulses: measurement of the recoil momentum by laser Doppler vibrometry
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Proceedings Volume 4961, Laser-Tissue Interaction XIV; (2003) https://doi.org/10.1117/12.477704
Event: Biomedical Optics, 2003, San Jose, CA, United States
Abstract
Currently ultra short pulses with pluse duration close to 100 fs are investigated for tissue ablation to perform laser surgery in a microscopic scale without any damage to the remaining tissue. Several groups showed already that the risk of thermal damage can be avoided; however the ablated material leaves the surface with a high velocity which leads to significant recoil momentum to the tissue. This paper focuses on the experimental set-up to measure this momentum transfer. Various set-ups had been developd over the last years like a pendulum that is highly senstive but cannot ensure that in a train of pulses each pulse will impact at exactly the same spot. A sliding rod in a glass tube ensured the constant impact point but is sensitive to several environmental conditions, which are hard to control. Recently, special swing plates were designed as vibration disks. The small sample was mounted in the center of this plate and exposed by fs pulses of a TiSa laser. The beam of a laser Doppler vibrometer was focused onto the backside of the plate monitored its motion. This set-up enabled us to measure the recoil momentum. While the total momentum transfer could be well determined to Δp=6 10-3 g mm/s, the question about a mechanical damage, for example for hair cells in the inner ear is much more difficult to answer, since this depends on the time in which the ablated materials leaves the surface. Evaporation times of 40 ps would lead to serious risk ofhar cell damage.
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Gaetano Sessa, Gaetano Sessa, Michele Travaglini, Michele Travaglini, Dirk Mittnacht, Dirk Mittnacht, Hans-Jochen Foth, Hans-Jochen Foth, } "Laser-tissue interaction with fs pulses: measurement of the recoil momentum by laser Doppler vibrometry", Proc. SPIE 4961, Laser-Tissue Interaction XIV, (27 August 2003); doi: 10.1117/12.477704; https://doi.org/10.1117/12.477704
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