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强激光通过光学系统聚焦于水下时,击穿水介质辐射强声波信号。光学聚焦特性的不同,使得激光击穿区域形状的差异,导致辐射的声信号在强度、频谱特征上具有较大的差异性。为研究不同光聚焦状态对激光击穿形成的空泡辐射声波的影响,推导了不同聚焦状态下激光空泡壁的运动方程及声辐射模型,构建了激光声实验测量系统,实验研究了不同聚焦状态下光击穿导致的空泡脉动参数、辐射声信号特征的差异性。结论:激光声信号强度与激光能量成线性关系,在激光能量高于一定参数情况下,声信号强度变化不大;在低激光功率下,扩束聚焦与非扩束聚焦,辐射的声信号特性差异不大;在高激光功率条件,扩束聚焦击穿形成的空泡半径大于非扩束聚焦击穿,辐射的声信号强度高于非扩束聚焦;为提高激光击穿辐射声信号效率,应对激光束进行扩束聚焦。
Strong laser through the optical system focused on underwater, the breakdown of the water medium radiation strong acoustic signal. The difference of the optical focusing characteristics makes the difference of the shape of the laser breakdown region, resulting in the great difference in the intensity and the frequency spectrum of the radiated sound signal. In order to study the influence of different light focusing states on the radiation wave of the bubble formed by the laser breakdown, the equations of motion and acoustic radiation model of the laser cavity wall under different focusing states were deduced. The experimental system of laser sound experiment was established. The state of light breakdown caused by the bubble parameters, the characteristics of radiated sound signal differences. Conclusions: The linear relationship between laser acoustic signal intensity and laser energy is linear. When the laser energy is higher than a certain parameter, the acoustic signal intensity does not change much. Under low laser power, the characteristics of acoustic signal At the condition of high laser power, the radius of the bubble formed by beam expansion is greater than that of non-beam expanding. The intensity of the acoustic signal is higher than that of the non-beam expanding. In order to improve the efficiency of the laser penetrating radiation signal, The laser beam should be beam expander focused.