Review of optical diagnosis methods for the laser produced plasmas

Laser produced plasma (LPP) is the research hotspot for several industrial applications. However, the understanding of the plasma dynamics is still far from satisfactory, and calls for more comprehensive study. Consequently, the optical diagnostics methods for laser produced plasmas are reviewed. The basic principles and techniques of ICCD and streak camera based fast photography, optical emission spectroscopy, laser shadowgraphy and schileren photography, laser interferometry, as well as Thomson scattering are introduced, respectively, from various angles of radiation detection, key parameters calculation, and the spatial refracitve index distribution. The advantages and limitations for different methods are compared. Considering the characteristics of laser produced plasma, special cares that should be taken of are pointed out, respectively, corresponding to the different techniques. The chosen bases of the laser parameters for the laser shadowgraphy, schlieren and interferometry are explained. The typical results of several diagnostics are presented and analyzed. Finally, the further advice for the present study is proposed.The results show that the fast photography is helpful for the direct visualization of the LPP dynamics, while the spectroscopic diagnostic is a convenient way to obtain the plasma parameters. Through the analysis of the LPP refractive index field by laser probe, the spatial density distribution could be expected. More accurate and abundant plasma microscopic information could be revealed by the Thomson scattering. It should be noted that the condition of thermal equilibrium status of the LPP should be considered when the optical emission spectroscopy is utilized, while the laser probe parameters, such as the laser wavelength, laser energy as well as the laser duration, should be chosen reasonably based on the specific condition of the plasma object. In the future work, through the combination of the different diagnostic methods, the spatio-temporal evolution of the multiple components in LPP, as well as the microscopic equilibrium status should be explored.