Fig. 1. Comparison of ultrashort pulse energy and average power indicators among state-of-the-art and anticipated science needs^[14]

Fig. 2. Operating principle of ICAN system^[34](① is seed source of ultrafast laser, ② is pulse broadening, ③ is beam splitter, ④ is multi-channel cascade amplification, ⑤ is pulse compression,⑥ is lens focusing, and ⑦ is output)

Fig. 3. Experimental setup of coherent beam combination of 61-channel ultrafast fiber lasers^[39]

Fig. 4. Schematic of coherent polarization beam combination^[42]

Fig. 5. Schematic of passive coherent beam combination of ultrafast laser based on Sagnac interferometer^[46]

Fig. 6. Experimental setup of spatially coherent beam combination of 12 filled aperture channels of ultrafast fiber laser with total output power of 10 kW level^[64]

Fig. 7. Schematic of spatially coherent beam combination of 16 filled aperture channels of multicore fiber laser^[70]

Fig. 8. Schematics of divided-pulse with polarization directions of pulse sequences shown by arrows^[46]. (a) Based on birefringent crystals; (b) based on polarization beam splitters and spatial delay lines

Fig. 9. Schematic of C-DPA principle based on one-way amplification^[79]

Fig. 10. Schematics of SnD^[82].(a) Schematic of coherent pulse stacking principle based on SnD; (b) schematic of evolution of pulse energy stored in SnD oscillation cavity with number of injected pulses

Fig. 11. Schematic of GTI oscillation cavity^[85]

Fig. 12. Structural diagrams of cascaded GTI oscillation cavities^[85]. (a) m GTI oscillation cavities; (b) m × m GTI oscillation cavities

Fig. 13. Experimental setup of spatio-temporally coherent beam combination of ultrafast fiber laser to achieve ultra-high average power and peak power^[82]

Fig. 14. Experimental setup of spatio-temporally coherent beam combination of ultrafast laser based on 4 temporal divided-pulses and 8 spatially combined filled aperture channels ^[95]

Fig. 15. Experimental setup of coherent beam combination of two filled aperture channels of ultrafast laser^[106]

Fig. 16. Schematic of passive coherent beam combination of two channels of ultrafast laser based on Sagnac interferometer^[114]