Radially polarized beams exhibit interesting properties for material processing, as well as for different scientific applications such as optical trapping, plasmon excitation or data storage. With a thin-disk multipass amplifier radially polarized ultra-short pulses with an average output power of 635 W were demonstrated in . For 100 W class operation, single-crystal fiber (SCF) amplifiers are an alternative approach to the thin-disk architecture. This approach reduces the costs and the complexity of the overall laser system significantly. The highest average output power demonstrated with an SCF amplifier was 160 W for a linearly polarized Gaussian seed beam  and 85 W for a ring-shaped radially polarized seed beam . In this contribution, we present the amplification of a ring-shaped radially polarized seed beam in a single-stage SCF amplifier to an average output power of 290 W in continuous-wave (CW) operation and 270 W in femtosecond pulsed operation. This is, to the best of our knowledge, the highest average output power of a radially polarized beam demonstrated so far with an SCF amplifier.
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