Fig. 1. Positional relationship between the linear array detector and the femtosecond filament

Fig. 2. Photoacoustic pressure signals induced by single filament received by transducers at different positions. (a) Time domain waveform; (b) Frequency spectrum

Fig. 3. Reconstructed photoacoustic axial images of single filament. (a) Original image; (b) Reconstruction result of UBP algorithm; (c) Reconstruction result of DAS algorithm; (d) Reconstruction result of SPANNER algorithm

Fig. 4. [in Chinese]

Fig. 4. Effect of different detection distances D on single filament reconstruction results. (a) D= 2 mm; (b) D= 4 mm; (c) D= 6 mm

Fig. 5. Distribution of original multi-filament arrangement

Fig. 6. Photoacoustic pressure signals induced by multi-filament received by transducers at different positions. (a) Time domain waveform; (b) Frequency spectrum

Fig. 7. Reconstructed photoacoustic axial images of multiple filament. (a) Reconstructed results of UBP algorithm; (b) Reconstructed results of DAS algorithm; (c) Reconstructed results of SPANNER algorithm

Fig. 8. Effect of different detection distances D on reconstruction results of multi-filament. (a) D= 2 mm; (b) D= 4 mm; (c) D= 6 mm