Fig. 1. Zig-zag optical path schematic

Fig. 2. 4f image transfer system. （a） Optical path schematic of transmissive image system；（b） optical path schematic of reflective image system

Fig. 3. Spherical aberration comparison of reflective and transmissive system

Fig. 4. Optical path schematic of Yb slab laser system

Fig. 5. Experimental results. （a）Spot distribution of seed source；（b）spot distribution at the entrance of the slab

Fig. 6. Schematic of amplifier gain module

Fig. 7. Experimental results. （a）Intensity distribution of pump source； （b） fluorescence distribution in the slab

Fig. 8. Output power and optical-to-optical efficiency variation curves with pump power

Fig. 9. Near-filed wavefront when output power is 7.13 kW

Fig. 10. β changes with time when output power is 7.13 kW