170-W picosecond optical vortex beam amplification in an all-fiber MOPA system.

We report the generation of high-average-output-power picosecond-pulsed optical vortex beams from an all-fiberized Yb-doped fiber master oscillator power amplifier (MOPA) system. A home-made broadband long-period fiber grating is employed as an in-line mode converter prior to the final power amplifier stage to efficiently convert the pre-amplified fundamental Gaussian beam into optical vortex beams with a topological charge of l=±1. The desired vortex beam is then efficiently amplified to an average output power of 170 W with a pulse duration of ~95 ps and a mode purity of ~92% at a repetition rate of 37 MHz, corresponding to a peak power of 48 kW. To the best of our knowledge, this represents the highest average power achieved for pulsed vortex beams generated entirely within an all-fiber system, providing a compact, alignment-free route to generate high-power optical vortex beams.