Acoustic Tests in a Micro Space based on a Point Source Generated by Laser-Induced Breakdown

提出了一种基于激光在空气中击穿产生的点源进行声振测试的方法。该系统采用高功率脉冲激光产生激光诱导的声场击穿。当激光束的局部光强达到1e+15W/m2时，可以通过激光诱导击穿实现等离子体的形成。通过消耗一部分等离子体能量而产生的冲击波成为声源。假设激光束通过凸透镜聚焦到小体积，并且激光诱导击穿的声源具有非方向性，利用这种技术可以产生点源。保护激光光路不会在声场中安装用于声激励的设备。通过比较激光击穿测量的微空间谐振频率和理论模型计算的微空间谐振频率，验证了该系统的有效性。

This paper proposes a method of acoustic vibration testing based on a point source generated by laser-induced breakdown in the air. A high-power Nd: YAG pulse laser is used in this system for generating the laser-induced breakdown in acoustic fields. Plasma formation can be realized by the laser-induced breakdown if the local intensity of the laser beam reaches 1e+15 W/m2. The shock wave that is yielded by consuming a part of the plasma energy becomes a sound source. Assuming that the laser beam is focused to a small volume through a convex lens and the sound source by the laser induced-breakdown has nondirectional property, it is possible to create a point source with this technique. Securing the laser light path installs no device for acoustic excitation in acoustic fields. The system is validated by comparing the resonant frequencies of a micro-space measured by the laser-induced breakdown and calculated by theoretical model.