Effects of focusing geometries and detection methods on LIBS of an aluminum target

Effective breakdown and signal detection are the goals of laser-induced breakdown spectroscopy (LIBS) optical systems, essential for promoting LIBS measurements. The focusing geometry and detection method have a certain influence on the line intensity of laser-induced breakdown spectroscopy. It has been shown that focusing without a beam expander results in an enhancement of the line intensity by more than 10 times compared to focusing with a beam expander. The detection of the entrance slit of the spectrometer provides an accurate comparison of the two focusing geometries. While the optical fiber endface offers a wide range of reception angles, enabling it to absorb more plasma emissions and reduce signal loss. Additionally, the large detection angle makes the spectral line intensity enhanced by 3 - 4 times compared to the horizontal detection. When detecting by the optical fiber, a larger detection angle is recommended to obtain superior LIBS signals. The effective breakdown and signal detection methods identified in the study provide technical support for improving line intensity and achieving effective detection of LIBS measurements of solid samples, which makes the LIBS technique have great potential for application in the field of analysis.