Power Scaling of Linearly Polarized Random Fiber Laser

The power scaling of linearly polarized random fiber lasers (RFLs) is investigated in detail based on master oscillator power amplifier configuration. A 442-W linearly polarized output with a narrow 3-dB linewidth of 0.28 nm and a 621-W linearly polarized output with a relatively wider 3-dB linewidth of 2.7 nm are realized. Besides, near-diffraction-limited beam quality and high polarization extinction ratio are obtained in both situations, and further power scaling is limited by the onset of mode instability (MI). To the best of our knowledge, these results are highest output powers of linearly polarized RFLs for the time being, in the narrow-linewidth and wide-linewidth situations, respectively. Meanwhile, the differences in the spectral broadening factor and the MI threshold between the narrow-linewidth linearly polarized RFL and the wide-linewidth one are discovered and discussed for the first time. It is experimentally demonstrated that relatively wider linewidth of the RFL seed is in favor of reducing the spectral broadening and increasing the MI threshold, providing significant reference for power scaling of linearly polarized RFL.