中文摘要：

为了改善激光声信号的特性，设计了激光声换能器。对换能器的设计原理和结构进行了说明。构建了激光声实验系统，利用脉冲激光分别在自由场和换能器内部聚焦击穿水介质产生声信号，由水听器将声信号转换成电信号并送入数字存储示波器。对两种条件下产生的激光声信号特性进行了比较。结果表明：同自由场产生的激光声信号相比，利用换能器产生的激光声信号特性有了一定程度的改善。其中，信号峰值幅度提高了3倍，能量向60 kHz以下频段集中，1 m处发散角压缩到13.2o，衰减速度变慢。

英文摘要：

For improving the quality of laser-induced acoustic signals, the laser-induced acoustic signal transducer was designed, its design theory and structure was analyzed and depicted. Experimental system was built. The pulsed laser was focused into water inside the transducer and in the free field respectively. A hydrophone was used to receive the acoustic signal and convert it into electric signals, a oscilloscope was connected with the hydrophone to display the signals. Laser-induced acoustic signals produced in two different environments have been compared. The results are as follows： compared with laser-induced acoustic signal produced in free field, that produced in the transducer has improved in its qualities. Peak pressures are 3 times larger. Signal energy is more concentrated below 60 kHz. Radiation angle has been decreased to 13.2o in 1 m distance. Signal attenuation gets slower.