Study Of Laser-induced Surface Micro-structures And Enhancement Effect Of Laser-induced Plasma

Laser-induced plasma(LIP)has a wide range of applications in signal detection,industrial production,food safety,environmental inspection,archaeological relics,space exploration and other fields.However,LIP still has some disadvantages such as poor detection limits,low measurement accuracy,low stability and so on.Therefore,enhancing the intensity of plasma has become an urgent problem to be solved at present.In this paper,nanosecond laser is used to produce periodical surface structures on silicon in order to promote the absorption rate and energy coupling efficiency of silicon,thereby enhancing the intensity of LIP on silicon.The main work of this research is concluded as follows:1.A 532 nm nanosecond laser is used to produce periodical surface structures on a silicon target,and the effects of different laser parameters(energy density,pulse number,repetition frequency,polarization state and wavelength)on the laser-induced periodical surface structures(LIPSS)are studied.The results show that the fluence,number of pulses and repetition rate have a large effect on the LIPSS morphology and almost no effect on the period size,and the LIPSS orientation is always perpendicular to the laser polarization direction.The dependence of the LIPSS period size on the laser incident angle is also investigated,and the results show that the incident angle significantly affects the LIPSS period size,which is in agreement with the results of the standard surface plasmon polaritons(SPPs)model.Finally,the parameter range of 532 nm nanosecond LIPSS generation on silicon is summarized.2.A high spatio-temporal resolution laser-induced plasma imaging platform is built,and the image resolution of the system is improved by optimizing the image transfer module.The dynamic evolution process of LIP of silicon in vacuum and a certain background pressure is further investigated.In vacuum,the effect of different roughness of silicon target on the intensity of plasma is investigated,and the results show that the greater the surface roughness,the higher the plasma intensity.Under the background pressure of 200 Pa argon gas,the plasma interacts with the background gas to produce shock wave.The Sedov-Taylor model is used to fit the shock wave propagation distance data at different times,and the shock wave energy is reversed based on the fitting results..The results show that the greater the surface roughness of the silicon target,the greater the energy carried by the laser-induced plasma shock wave.