Optoacoustic lenses are used for focusing and generation of mechanical waves, which is particularly useful in biomedicine for the diagnosis and treatment of soft tissues. Short laser pulses are used for causing short-term ablation and repulsion of the substance in the direction of wave propagation on the surface of the lens. In the master 's thesis, we investigated laser - excited optoacoustic phenomena using a titanium lens. We found that at sufficiently high laser pulse energies, cavitation bubbles appear, which have similar dynamics in both agar and water samples. The oscillation times of cavitation bubbles in agar are significantly shorter compared to the oscillation times of cavitation bubbles in water (20 μs for agar and 250 μs for water). The minimum laser pulse energy for cavitation bubbles in agar is 350 mJ. As with water samples, the growth of cavitation bubbles is linearly related to the growth of laser pulse energy. We found that at lower energies and successive shots in the same point, the amount of cavitation cloud decreases, and that barycentre of the rectangle cavitation cloud changes rapidly after the first consecutive shot and then stabilizes.
|
