Huang Shanmin, Hao Xiulu, Li Haobo, Fan Chenchen, Chen Xiao, Yao Tianfu, Huang Liangjin, Zhou Pu
College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China.
Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China.
Micromachines (Basel). 2024 Oct 7;15(10):1237. doi: 10.3390/mi15101237.
Raman fiber lasers (RFLs), which are based on the stimulated Raman scattering effect, generate laser beams and offer distinct advantages such as flexibility in wavelength, low quantum defects, and absence from photo-darkening. However, as the power of the RFLs increases, heat generation emerges as a critical constraint on further power scaling. This escalating thermal load might result in transverse mode instability (TMI), thereby posing a significant challenge to the development of RFLs. In this work, a static model of the TMI effect in a high-power Raman fiber amplifier based on stimulated thermal Rayleigh scattering is established considering higher-order mode excitation. The variations of TMI threshold power with different seed power levels, fundamental mode purities, higher-order mode losses, and fiber lengths are investigated, while a TMI threshold formula with fundamental mode pumping is derived. This work will enrich the theoretical model of TMI and extend its application scope in TMI mitigation strategies, providing guidance for understanding and suppressing TMI in the RFLs.
拉曼光纤激光器（RFL）基于受激拉曼散射效应产生激光束，并具有诸如波长灵活性、低量子缺陷和无光暗化等显著优点。然而，随着拉曼光纤激光器功率的增加，发热成为进一步提高功率的关键限制因素。这种不断增加的热负载可能导致横向模式不稳定性（TMI），从而对拉曼光纤激光器的发展构成重大挑战。在这项工作中，考虑高阶模式激发，建立了基于受激热瑞利散射的高功率拉曼光纤放大器中TMI效应的静态模型。研究了不同种子功率水平、基模纯度、高阶模式损耗和光纤长度下TMI阈值功率的变化，同时推导了基模泵浦的TMI阈值公式。这项工作将丰富TMI的理论模型，并扩展其在TMI缓解策略中的应用范围，为理解和抑制拉曼光纤激光器中的TMI提供指导。
