Development of miniaturized SAF-LIBS with high repetition rate acousto-optic gating for quantitative analysis

The self-absorption effect in laser-induced breakdown spectroscopy (LIBS) reduces the accuracy of quantitative measurement results. The self-absorption-free LIBS (SAF-LIBS) has been proved to directly capture the optically thin plasma spectra by setting an appropriate exposure time. In this work, a novel SAF-LIBS technique with high repetition rate acousto-optic gating is developed, in which an acousto-optic modulator is used as the shutter to diffract the optically thin fluorescence, and a high repetition rate laser is used to produce quasi-continuous plasmas to enhance the integral spectral intensity, so that the CCD spectrometer can replace an intensified CCD (ICCD) and echelle spectrometer in SAF-LIBS. Experimental results show that the average absolute prediction error of aluminum is reduced to 0.18%, which is equivalent to that of traditional SAF-LIBS. This technique not only effectively shields continuous background radiation and broadened spectral lines in optically thick plasma, but also has advantages of miniaturization, low cost, convenience and reliability.