Improving the detection sensitivity of mu LIBS with second excitation by orthogonal target-plasma

Micro-laser-induced breakdown spectroscopy (mu LIBS) has very important applications in elemental microanalysis of different samples. However, with the decreasing of ablated sample mass and plasma temperature, the detection sensitivity of RUBS will decrease significantly. In order to solve this problem, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) using an aluminum target was investigated in this work. In the experiments, 532 nm laser pulses with 12 ns pulse width were focused on the brass sample surface by a 10x microscope objective to ablate the sample; time-delayed 1064 nm reheating laser pulses with 12 ns pulse width were focused on the surface of an aluminum target to produce target plasma. The ablated sample was reheated and further broken down by this orthogonal target plasma and enhanced atomic emissions of the sample elements could be observed. The emission spectra were recorded with a compact spectrometer coupled with non-intensified charge-coupled device (CCD) detectors. The intensities of the optical emissions of the sample elements in mu LIBS, ODP-LIBS as well as TEODP-LIBS were compared. Up to 3 orders and 16-folds signal enhancement have been observed in TEODP-LIBS if compared with mu LIBS and ODP-LIBS, respectively. It is demonstrated that TEODP-LIBS is able to give much higher enhancement factor on the signal intensity than ODP-LIBS. TEODP-LIBS is able to significantly improve the detection sensitivity of RUBS under minimal sample ablation and find important applications on the elemental microanalysis of different samples.