The combination of laser-induced breakdown spectroscopy based on fiber lasers (FL-LIBS) and non-gated detectors takes advantages of cost-effective, fast response, and stable long-term operation, has great potential for rapid detection and online diagnosis. However, conventional calibration-free (CF) method struggle to achieve satisfactory analytical accuracy in FL-LIBS measurements with such detectors. This is because the plasma properties certainly change during the acquisition time which is much longer than plasma lifetime. Therefore, this work develops a novel calibration-free method to address the limitations in FL-LIBS using non-gated detectors. The methodology comprises two principal components: spectra simulation via time-integration method and determination of unknown parameters utilizing particle swarm optimization (PSO); hence, the new calibration-free method is designated as PSO-SSCF. Overall, it exhibits superior accuracy on the quantitative analysis of standard TC4 titanium alloys. Compared to conventional CF method, reductions in average relative errors (AREs) range from 1.539% to 7.631% for aluminum, 22.631% to 29.173% for vanadium, and −1.071% to 0.714% for titanium. PSO-SSCF even outperforms the time-integrated calibration-free (TICF) method with an iCCD gated detector. Moreover, PSO-SSCF shows good repeatability with relative standard deviation (RSD) less than 5%, and achieves sub-second computation time via GPU acceleration. In a summary, this work provides a feasible calibration-free method for FL-LIBS, facilitating the application of LIBS in scientific and industrial fields.
Lin et al. (Thu,) studied this question.