Quantitative analysis improvement of laser-induced breakdown spectroscopy based a newly beam shaping method.

The relatively high uncertainty and poor sensitivity of Laser-induced breakdown spectroscopy (LIBS) signals are the challenging task for its large-scale commercialization, due to the matrix effects, self-absorption effect and other environmental factors. LIBS combined with beam shaping method is a simplicity and low-cost way to improve its quantitative analysis performance. However, the essential optic equipment diffractive optical element (DOE) is still expensive and is only applied in laser beam with specific parameters. In this work, we design a newly beam shaper consisting of plano-concave cylindrical lens and plano-convex cylindrical lens to change energy distribution of Gaussian beam (GB). The shaped beam with a more homogeneous energy distribution, called approximately flat-top beam (AFTB), was expected to improve LIBS analysis capability by improving ablation efficiency and reducing the plasma shielding effect, which would enhance signal intensity and reduce signal uncertainty. The results showed that the determination coefficients (R) of all trace elements in steel alloy samples are improved over 0.9658, and the root-mean-square-error (RMSE), the average relative error (ARE) of partial calibration curves are nearly reduced to a half and fifth of these. The almost all limits of detection (LOD) of AFTB remain a slightly lower value than that of GB. These results indicate our proposed beam shaping method has a good potential to improve the LIBS analytical ability.