ABSTRACT
The acoustic signal of the laser micro plasma expansion for the femtosecond laser when ablating a silicon wafer has been detected using the whole optical fiber sensing probe. Meanwhile, a high-speed CCD camera has been applied to observe the expansion process of the laser micro plasma. In comparison, the frequency and amplitude of the acoustic emission spectrum has been analyzed, and the dynamic characteristics of the femtosecond laser micro plasma expansion have been researched. The results show that the detected acoustic emission signal frequency spectrum pattern is fixed with changing the laser energy. The amplitude of the acoustic emission spectrum decreases along with the increasing of the detection distance. Further analysis of the continuous 10 ms acoustic emission signal frequency spectrum found that the acoustic emission signal amplitude of the plasma dynamic expansion process increased first, and then decreased under the same conditions of the femtosecond laser energy and the detection distance. The rule conforms to the dynamic process from the high-speed CCD.
