Here, we present very low pulse energies (below 200 nJ) at very high speed (over 100 kHz) LIBS experiment by employing our recently developed 25 ps, 14W, 2.8 GHz intra-burst repetition rate Yb-doped fiber laser system. To carry out the LIBS experiments, the laser beam is directed into a Galvo scanner and focused through a 56 mm long F-theta lens onto different materials, including steel, copper, aluminum, and silicon. Our investigation of LIBS encompassed various parameters, including varying pulse energies, the number of intra-burst pulses, and burst repetition rates. For instance, with a burst repetition rate of 100 kHz with 83 ns burst width (232 intra-burst pulses), we observed the threshold pulse energy stands at approximately 26 nJ for LIBS experiment on steel. Furthermore, at about 200 nJ, it is enough to keep a high signal-to-noise ratio. To the best of our knowledge, this is the first report on LIBS experiment by GHz-range laser operating in the burst mode regime.
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