Fig. 1. Experimental setup of Yb:YAG slab MOPA chain. P-A, preamplifier; MA, main amplifier; BS, beam shaper; PM, power meter.

Fig. 2. (a) Schematic of CCEPS gain module; (b) detailed scheme of pump coupling and homogenization system; (c) and (d) distributions of pumping light at the middle of the slab and the entrance, respectively.

Fig. 3. Multi-concentration-doped slabs in the preamplifier and main amplifier.

Fig. 4. Micrograph of the end face of the slab. (a) and (b) 100 µm level and submicrometer level surface, respectively.

Fig. 5. Absorption rate of films. (a) and (b) Maximum absorption rate of 300 ppm and 20 ppm, respectively.

Fig. 6. Temperature comparison of the main amplifier slab end face. (a) and (b) Maximum temperatures of 110°C and 42°C, respectively.

Fig. 7. (a) Output power of MOPA chain and optical extraction efficiency of main amplifier; (b) comparison of the theoretical and experimental dependence of the output power and slope efficiency.

Fig. 8. (a) OPD of one passing through the slab at the maximum output power; (b) residual OPD after quadratic fitting to eliminate defocus.

Fig. 9. (a) Distribution of the expanded beam in the near field; (b) variation of output beam quality (β) in 0.5 min; (c) far field with the beam quality of 2.95.