Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot. At present, research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser. However, the suppression of spectral broadening, caused by self-phase modulation or four-wave mixing, is still a challenging attribute to the close distance between the broadened laser and signal laser. If using a traditional fiber grating with only one stopband to suppress the spectral broadening, the signal power will be stripped simultaneously. Confronting this challenge, we propose a novel method based on phase-shifted long-period fiber grating (PS-LPFG) to suppress spectral broadening in a high-power fiber master oscillator power amplifier (MOPA) laser system in this paper. A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique. The resonant wavelength of the fabricated PS-LPFG is 1080 nm, the full width at half maximum of the passband is 5.48 nm, and stopband extinction exceeds 90%. To evaluate the performance of the PS-LPFG, the grating is inserted into the seed of a kilowatt-level continuous-wave MOPA system. Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%, providing an effective and flexible way for optimizing the output linewidth of high-power fiber MOPA laser systems.

中文翻译：

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利用相移长周期光纤光栅抑制高功率光纤 MOPA 激光系统的光谱展宽

基于光纤光栅抑制大功率光纤激光器中的非线性效应已成为研究热点。目前，研究主要集中在抑制高功率光纤激光器中的受激拉曼散射。然而，由自相位调制或四波混频引起的光谱展宽的抑制仍然是展宽激光与信号激光之间距离较近的一个具有挑战性的属性。如果使用只有一个阻带的传统光纤光栅来抑制光谱展宽，信号功率将同时被剥离。面对这一挑战，我们提出了一种基于相移长周期光纤光栅（PS-LPFG）的新方法来抑制高功率光纤主振荡器功率放大器（MOPA）激光系统中的光谱展宽。PS-LPFG 采用逐点扫描技术在 10/130 无源光纤上设计和制造。制作的PS-LPFG的谐振波长为1080 nm，通带半高宽为5.48 nm，阻带消光超过90%。为了评估 PS-LPFG 的性能，将光栅插入到千瓦级连续波 MOPA 系统的种子中。实验结果表明，输出光谱的30 dB线宽缩小了约37.97%，为优化高功率光纤MOPA激光系统的输出线宽提供了一种有效且灵活的途径。为了评估 PS-LPFG 的性能，将光栅插入到千瓦级连续波 MOPA 系统的种子中。实验结果表明，输出光谱的30 dB线宽缩小了约37.97%，为优化高功率光纤MOPA激光系统的输出线宽提供了一种有效且灵活的途径。为了评估 PS-LPFG 的性能，将光栅插入到千瓦级连续波 MOPA 系统的种子中。实验结果表明，输出光谱的30 dB线宽缩小了约37.97%，为优化高功率光纤MOPA激光系统的输出线宽提供了一种有效且灵活的途径。