Abstract
We experimentally investigate the acoustic characteristic of micro plasma shock wave obtained by femtosecond laser ablation of silicon wafer surface using F-P optical fiber acoustic sensor with anti electromagnetic interference. The experimental results show that each of the femtosecond laser pulse can only produce a plasma shock wave. Under the different femtosecond laser energy, the acoustic attenuation signal of single shock wave has been analyzed by using wavelet transform, the results indicated that the energy change of femtosecond laser has no effect on the frequency of the acoustic signal of the micro plasma shock wave and have only influence on the amplitude, meanwhile, the main frequency of the acoustic attenuation signal are distributed within range of 0-100KHz, According to these frequency components, we can conclude that the decay process of micro plasma shock wave is the fast transduction of the ultrasonic signal into the acoustic signal. This study can provide the experimental basis for femtosecond laser ablation mechanism and femtosecond laser plasma control application research.
Highlights
Initiated new research paths for more detailed understanding of ultrafast laser-material interactions, plasma excited species expansion dynamics, and mechanisms of material removal[3]
The ablation process of different materials basically coincides with the threshold theory, still there is no clear understanding of the plasma dynamics characteristics and the interaction of femtosecond laser ablating different materials so far, and it is not even clear of the mechanism of its origin
We make a research on characteristics and the decay process of plasma obtained by femtosecond laser ablation target material, providing experimental basis for femtosecond laser ablation mechanism and plasma control
Summary
According to the existed experimental phenomena and results, people put forward different theories when dealing with different material, mainly including two-temperature model[5], micro explosion theory[6], theory of Coulomb explosion[7,8] and threshold theory[9]. The ablation process of different materials basically coincides with the threshold theory, still there is no clear understanding of the plasma dynamics characteristics and the interaction of femtosecond laser ablating different materials so far, and it is not even clear of the mechanism of its origin This field needs more theoretical and experimental research [10]. The latest new method has been proposed to investigate the optical emission features of plasmas by using time of flight emission spectroscopy, but the decay processes occur on a nanosecond time scale and are functions of plasma parameters such as electron density and temperature Measuring those parameters is difficult due to fast relaxation (1 ns), relatively low electron density. We make a research on characteristics and the decay process of plasma obtained by femtosecond laser ablation target material, providing experimental basis for femtosecond laser ablation mechanism and plasma control
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