Li Haobo, Wu Hanshuo, Yang Cheng, Ding Xinyi, Huang Liangjin, Pan Zhiyong, Wang Xiaolin, Zhou Pu
Opt Lett. 2025 Jan 15;50(2):511-514. doi: 10.1364/OL.546878.
Dynamic transverse mode instability (TMI) has become one of the primary limitations for power scaling of high-power fiber lasers. Experimental evidence has shown that static mode degradation can suppress the dynamic TMI effect. This study reveals the physical mechanisms behind the mitigation of dynamic TMI in two-mode fiber lasers through static mode degradation. Using a dynamic TMI model based on the two-beam coupling theory, we differentiate the impacts of relative intensity noise and the proportion of higher-order mode in the seed on TMI. Static mode degradation modifies the transverse gain distribution, thereby affecting the overlap between the thermally induced refractive index grating and the interference light field, which inhibits dynamic mode coupling. Our findings indicate that the effectiveness of this suppression is significantly influenced by the gain saturation. By enhancing gain saturation through strategies such as optimizing the pump injection direction, adjusting the pump wavelength, and reducing the core-to-cladding ratio, the suppression of TMI can be maximized, which is essential for advancing the performance and stability of these laser systems.
动态横向模式不稳定性（TMI）已成为高功率光纤激光器功率提升的主要限制因素之一。实验证据表明，静态模式劣化可以抑制动态TMI效应。本研究揭示了通过静态模式劣化减轻双模光纤激光器中动态TMI的物理机制。利用基于双光束耦合理论的动态TMI模型，我们区分了相对强度噪声和种子光中高阶模比例对TMI的影响。静态模式劣化改变了横向增益分布，从而影响热致折射率光栅与干涉光场之间的重叠，抑制了动态模式耦合。我们的研究结果表明，这种抑制效果受到增益饱和的显著影响。通过优化泵浦注入方向、调整泵浦波长和减小纤芯与包层比等策略增强增益饱和，可以最大限度地抑制TMI，这对于提高这些激光系统的性能和稳定性至关重要。
