一种跨介质的空中-水下激光致声探测技术研究

跨空水介质间的探测技术是世界主要海洋国家的热点研究问题。为研究空中平台与水下的激光致声探测技术，文中在光击穿机制下采用纳秒脉冲激光与水听器之间的光声信号转换来进行空-水跨介质探测模拟实验研究及验证工作。搭建了激光致声空气-水下实验测试系统，采集了激光声扫描探测数据，对典型实验数据在时域内进行分析得出了激光激励声波的传播特性，根据时间互易原理实现了水下激光声信号的三维探测成像。利用有限元法进行激光在水下激发声波及传播的数值仿真，据此对实验进行了验证。此外，从仿真中发现通过提高脉冲能量至2.8×1010 W/cm2所激励的声波在传播400 m后仍能观测出明显的信号，信噪比约为11.3 dB，证明了百米级传输及探测的可能性。此研究结果为采用激光致声技术进行跨空-水介质探测提供了依据。

Research on laser induced acoustic detection of trans-media aerial-underwater

Remote detection technology between air platform and underwater is a hot research issue in the marine countries. The aim of the present work is to study the laser induced acoustic (LIA) technology used for the detection from air to underwater. The experiment and simulation of LIA detection based on the mechanism of laser-induced breakdown were mainly described. Nanosecond pulse laser was used to generate acoustic wave by the photoacoustic conversion, and the hydrophone was used to receive the waves. LIA scanning data was collected to analyze the character of acoustic source underwater by using the setup above. Then 3D imaging of LIA underwater was carried out based on the time reciprocity principle. Simulations of the sound waves generation and propagate underwater was performed by finite element method. Furthermore, it is observed from the simulation that sound signal can be still obtained after it propagates 400 m, when the laser energy increases to 2.8×1010 W/cm2. The signal to noise ratio is about 11.3 dB. The simulation shows the possibility of detection by LIA underwater in hundred meters-level. The present study provides a method for the remote detection underwater across air-water media by using LIA technology.