Monolithic Linearly Polarized Nanosecond Fiber Laser with Record Peak Power and Near-Transform-Limited Linewidth

An all-fiberized linearly polarized nanosecond fiber laser with high peak power and near-transfrom-limited linewidth is demonstrated based on master oscillator power amplifier structure. Employing the polarization-maintaining large-mode-area Yb-doped fiber with tapered longitudinal geometry, short length and high concentration, the main amplifier possesses excellent performance for nonlinear effect suppression, including stimulated Brillouin scattering effect and self-phase modulation effect. As a result, an average output power of 8.8 W with the pulse duration of 3.8 ns is obtained at the repetition frequency of 80 kHz after the amplification, corresponding to the peak power of ~30 kW and the pulse energy of 110 uJ. The near- transform-limited linewidth is maintained, accompanying high polarization extinction ratio of more than 16 dB and near-diffraction-limited beam quality with M
²
factor of 1.2. It is known to be the record output power of all-fiber linearly polarized ns fiber laser with transform-limited linewidth, to the best of our knowledge.