title: 560  W all fiber and polarization-maintaining amplifier with narrow linewidth and near-diffraction-limited beam quality.
abstract: We present a narrow linewidth, all-fiber polarization-maintained amplifier chain seeded by a phase-modulated single-frequency laser, which is a narrow linewidth. Different from previous phase-modulation techniques, the phase-modulation signal is generated by simply imposing an excited signal to an acoustic-optical driven source. Theoretical simulation results show that this method can suppress stimulated Brillouin scattering (SBS) to a better degree, and the output power can be boosted to about 1.2 kW in terms of the SBS threshold. By amplifying the phase-modulated seed based on master-oscillator power-amplification configuration in experiments, a 560 W output laser is achieved with slope efficiency of 87.2% and linewidth of <5  GHz. Further power scaling is limited by mode instability instead of an SBS effect. At maximal output power, the beam quality (M2factor) and polarization extinction ratio is measured to be within 1.3 and 14 dB, respectively.
authors.forename: Yang
authors.initials: Y
authors.lastname: Ran
authors.forename: Rumao
authors.initials: R
authors.lastname: Tao
authors.forename: Pengfei
authors.initials: P
authors.lastname: Ma
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Wang
authors.forename: Rongtao
authors.initials: R
authors.lastname: Su
authors.forename: Pu
authors.initials: P
authors.lastname: Zhou
authors.forename: Lei
authors.initials: L
authors.lastname: Si