High brightness plasma source sustained by pulse laser

Laser-sustained plasma (LSP) source featured by high brightness and wide spectral range is found to be powerful in advanced inspection and spectroscopy applications. Brightness is the key indicator that determines the speed of semiconductor defect inspection. However, the spatial asymmetry of the laser power absorbed by the plasma drives it to grow in the direction of laser incidence, resulting in a decrease in plasma temperature, hence restricting the improvement of brightness. In this paper, we propose an innovative pulse laser-sustained plasma to break through the plasma temperature limitation. Driven by the elevated plasma temperature, the plasma emission power is significantly enhanced. We establish a two-dimensional transient fluid model for LSP to quantitatively construct the relationship between plasma temperature and laser characteristics. The evolution process of LSP is studied systematically through this model. For the first time, we report an important conceptual advance that the use of pulse laser suppresses the defocus displacement of the plasma, thus increasing the plasma temperature conspicuously. Experimental results demonstrate that the plasma emission is enhanced through the entire wavelength range and time period, compared with continuous laser with the same average power. Especially in the ultraviolet band (<400 nm), the enhancement of plasma emission exceeds 50%. This paper establishes a quantitative relationship between laser temporal characteristics and the spatial distribution of plasma temperature, providing theoretical support and experimental verification for achieving high brightness plasma light sources through laser temporal modulation.