Fig. 1. Schematic diagram of experimental setup for underwater LIBS detection on submerged solid target

Fig. 2. LIBS spectra of laser under laser energy of 20 mJ and different laser focus positions. (a) With 25 ns laser duration; (b) with 6 ns laser duration

Fig. 3. Contour maps of SNR and SBR as functions of laser energy and duration. (a) SNR; (b) SBR

Fig. 4. Comparison of spectral stability under different conditions. (a) Scatter plot of repeated LIBS signals intensity of Al I 396.1 nm before and after spectral preprocessing; (b) 3D contour map of RSD as a function of laser energy and duration after spectral preprocessing

Fig. 5. Shadowgraph images with 17 ns and 6 ns lasers obtained at different delays. (a) 100 ns; (b) 1 μs; (c) 50 μs; (d) 100 μs

Fig. 6. Three-dimensional images of ablation craters. (a) With 17 ns laser duration; (b) with 6 ns laser duration