Fig. 1. Schematic diagram of the eight-pass laser amplifier. (a) Optical layout. PBS, polarizing beam splitter; M1, M2, flat reflective mirrors; QWP, quarter-wave plate. (b) Sequence of the laser beam passing through the gain medium. (c) Propagation trajectory of the central ray in the gain module.

Fig. 2. Schematic diagram of the propagation of two types of rays in a grid. (a) Grid-matched ray. (b) Non-grid-matched ray.

Fig. 3. Scaling performance of the amplifier at the seed energy of 120 mJ.

Fig. 4. Experimental output energy versus input energy for the eight-pass amplifier, compared with the simulation results for two-pass, four-pass and eight-pass configurations, as well as the simulated eight-pass case without angular deviation.

Fig. 5. The calculation of g₀ in the x–z plane before and after energy extraction.

Fig. 6. The x-dimensional profile of g₀ averaged over z before and after energy extraction. BE, before extraction; AE, after extraction.

Fig. 7. Beam quality of amplified output (3 J, 50 Hz). (a) Measurement setup. (b) Beam wavefront. (c) Near-field pattern. (d) Far-field pattern.