Underwater holmium-laser-pulse-induced complete cavitation bubble movements and acoustic transients

The complete evolution of holmium-laser-pulse-induced cavitation bubble movements and acoustic transients underwater are investigated experimentally. The laser was single fiber-guided and had a 300 mJ pulse energy and 300 μs pulse duration (full width at half-maximum). In our experiments, more than four oscillations and four acoustic transients were demonstrated. 272 μs after laser onset, the cavitation bubbles reached their maximum transverse and longitudinal lengths of 2046 and 1914 μm, respectively. The maximum transverse and longitudinal bubble wall velocities were 28.9 and 39.2 m/s at 560 and 528 μs after laser onset, respectively. This investigation will be helpful to make good use of cavitation effect in medical applications of holmium laser pulses.

脉冲钬激光水下空化效应及消融生物硬组织动态特性

利用高速摄影术准确记录光纤传输的自由运转钬激光脉冲在水下产生空化泡及消融生物硬组织的动态变化进程,同时采用针式水听器探测空化泡闭合时辐射的振荡波信号。实验结果表明,空化泡谐振周期数至少达到4个,其谐振周期分别为368,144,56和40μs。在谐振进程中能量主要集中在第一个周期,空化泡形状逐渐变得更不规则,4次闭合时辐射的振荡波信号强度分别为20.5×105,12.6×105,5.1×105和2.0×105Pa。此外,生物硬组织表面水层除了可以提高消融效率外,还可显著提高消融凹坑表面光滑度。

基于高速摄影术的聚焦Nd:YAG脉冲激光水下空化效应实验研究

采用高速摄影术准确记录聚焦脉冲Nd:YAG激光水下诱导空化泡动态变化进程,同时采用针式水听器探测空泡闭合或等离子体膨胀时辐射的冲击波信号.实验结果表明,当针式水听器端面和聚焦点间距逐渐减小时,相同实验条件下,探测到的声学信号个数增多且信号强度增强.激光脉冲结构、能量、脉宽等激光参数直接决定单个激光脉冲诱导空泡个数、形貌以及等离子体膨胀和空泡闭合时辐射的声学信号特性.实验结果可为短脉冲激光在临床医学上的运用提供理论与实践支持.