Impact of amplified spontaneous emission noise on the SRS threshold of high-power fiber amplifiers

Impact of amplified spontaneous emission (ASE) noise on the stimulated Raman scattering (SRS) threshold of high-power fiber amplifiers is demonstrated numerically through a spectral evolution approach. The simulation results confirm that ASE noise in the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly. As for ASE noise originated the main amplifier, it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm. As for ASE noise originated from the seed laser, it reduces the SRS threshold at different operation wavelength under the condition that the Raman ratio is over –90 dB in the seed laser. The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.