Radially polarized picosecond MOPA system based on double-clad ytterbium-doped spun tapered fiber with ring-shaped active core

We have demonstrated for the first time, to the best of our knowledge, the successful direct amplification of a cylindrical-vector beams with axially symmetric polarization and doughnut-shaped intensity profile in picosecond MOPA system based on a double-clad ytterbium-doped spun tapered fiber with a ring-shaped active core. The output radially polarized beam with absolute contrast between bright and dark zones carries 10 ps pulses at 1030 nm with a 14.5 W average power level, 91 kW peak power and 0.97 μJ pulse energy.