Jiao Kerong, Shen Hua, Guan Zhiwen, Yang Feiyan, Zhu Rihong
Opt Express. 2020 Mar 2;28(5):6048-6063. doi: 10.1364/OE.384760.
Two long-period fiber gratings (LPFGs) used to separately suppress the stimulated-Raman-scattering (SRS) in the seed and amplifier of kW-level continuous-wave (CW) MOPA fiber laser are developed in this paper. A process that combines constant-low-temperature and dynamic-high-temperature annealing was employed to reduce the thermal slopes of 10/130 µm (diameter of core/cladding fiber) and 14/250 LPFGs, used in the seed and amplifier respectively, from 0.48 °C/W to 0.04 °C/W and from 0.53 °C/W to 0.038 °C/W. We also proposed a reduced-sensitivity packaging method to effectively reduce the influence of axial-stress, bending, and environmental temperature on LPFGs. Further, we established a kW-level CW MOPA system to test SRS suppression performance of the LPFGs. Experimental results demonstrated that the SRS suppression ratios of the 10/130 and 14/250 LPFGs exceed 97.0% and 99.6%, respectively.
本文研制了两种长周期光纤光栅（LPFG），用于分别抑制千瓦级连续波（CW）主振荡功率放大器（MOPA）光纤激光器种子源和放大器中的受激拉曼散射（SRS）。采用恒定低温与动态高温退火相结合的工艺，分别将种子源和放大器中使用的10/130 µm（纤芯/包层光纤直径）和14/250 LPFG的热斜率从0.48℃ /W降低到0.04℃ /W，从0.53℃ /W降低到0.038℃ /W。我们还提出了一种降低灵敏度的封装方法，以有效降低轴向应力、弯曲和环境温度对LPFG的影响。此外，我们建立了一个千瓦级连续波MOPA系统，以测试LPFG的SRS抑制性能。实验结果表明，10/130和14/250 LPFG的SRS抑制率分别超过97.0%和99.6%。
