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为了对激光等离子体声信号特性进行深入研究,构建了激光声实验系统。使用波长1.06μm Nd:YAG脉冲激光聚焦击穿水介质产生激光等离子体声信号,使用水听器对信号进行接收,通过高速摄像机对信号产生过程进行了记录。分析了激光等离子体声信号的时频域特征。从理论上研究了激光等离子体声信号的指向性和传输特性,并进行了实验验证。研究结果表明:激光等离子体声信号时域脉宽为15μs左右,频带宽度为200kHz,主频在70kHz左右。信号在不同传输角度上的幅度差异很小,按照近似1/r的规律衰减,传输过程中主频逐渐减小。
In order to further study the acoustic characteristics of laser plasma, a laser acoustic experiment system is constructed. The Nd: YAG pulsed Nd: YAG pulsed laser was used to produce a laser plasma sound signal by using a laser beam to penetrate the aqueous medium. The signal was received by a hydrophone and the signal generation process was recorded by a high-speed camera. The time-frequency characteristics of the laser plasma acoustic signal are analyzed. The directivity and transmission characteristics of the laser plasma acoustic signal have been studied theoretically and experimentally verified. The results show that the pulse width of the laser plasma acoustic signal in the time domain is about 15μs, the frequency bandwidth is 200kHz and the dominant frequency is about 70kHz. The difference in the amplitude of the signal at different transmission angles is very small, decaying in accordance with the law of approximately 1 / r, and the dominant frequency gradually decreases during the transmission.