Hybrid inno-zigzag slab amplifier delivers 140× gain for 1 kHz high-energy picosecond pulses

We report a novel, to the best of our knowledge, inno-zigzag slab laser amplifier that innovatively combines features of innoslab and zigzag slab amplifiers. Operating at 1 kHz repetition rate, this architecture amplifies 300 ps pulses from 0.4 mJ to 57.5 mJ with a gain factor of 143.8. The seed laser undergoes eight-pass amplification through multiple total-reflection folded paths and inclined propagation within the gain medium, achieved by injecting at varied incident angles. The zigzag beam folding simultaneously increases the total gain path length and enables repeated energy extraction in total reflection regions. This configuration effectively homogenizes the temperature gradient along the thickness direction, mitigating wavefront distortion while enhancing beam quality in the thickness dimension. The beam quality of the output laser is M_x² = 1.19, M_y² = 1.42. To the best of our knowledge, this is the only report of the first use of a novel inno-zigzag slab structure that provides 140 times gain to output a high-energy picosecond pulsed laser.