625 mJ, 1 kHz picosecond pulsed laser amplifier based on cascaded zig-zag slabs

We report a 1 μm zig-zag slab laser amplifier producing 625.4 mJ pulses at repetition of 1 kHz, with pulse duration of 477 ps. A two-stage end-pumped Nd:YVO₄ pre-amplifier raises the pulse energy from a Q-switched microchip laser from 400 μJ to 7.47 mJ. After beam shaping using a super-Gaussian seed profile at a tailored propagation distance, the beam is amplified in a two-stage zig-zag slab amplifier. By analyzing thermal wavefront distortion and optimizing the incident angle and aperture ratio, the main amplifier is constructed with angular multiplexing (20.91° and 26.19°) and polarization control. The measured beam quality factors were M_x² = 1.73 and M_y² = 3.34. With a simple end-pumped Nd:YVO₄ and zig-zag slab architecture, pulse energy is increased by three orders of magnitude. It provides a valuable reference for the development and application of high-energy picosecond laser technology operating at kHz repetition rates.