Lin Wei, Wang Wenlong, He Bin, Chen Xuewen, Hu Xu, Guo Yuankai, Xu Yue, Wei Xiaoming, Yang Zhongming
Opt Express. 2021 Apr 12;29(8):12049-12065. doi: 10.1364/OE.423811.
The existence of vector solitons that arise from the birefringence nature of optical fibers has been increasingly of interest for the stability of mode-locked fiber lasers, particularly for those operating in the high-fundamental-repetition-rate regime, where a large amount of fiber birefringence is required to restore the phase relation between the orthogonally polarized vector solitons, resulting in stable mode-locking free of polarization rotation. These vector solitons can exhibit diverse time-varying polarization dynamics, which prevent industrial and scientific applications requiring stable and uniform pulse trains at high fundamental repetition rates. This pressing issue, however, has so far been rarely studied. To this end, here we theoretically and experimentally dissect the formation of vector solitons in a GHz-repetition-rate fiber laser and investigate effective methods for suppressing roundtrip-to-roundtrip polarization dynamics. Our numerical model can predict both dynamic and stable regimes of high-repetition-rate mode-locking by varying the amount of fiber birefringence, resulting in the polarization rotation vector soliton (PRVS) and linearly polarized soliton (LPS), respectively. These dynamic behaviors are further studied by using an analytical approach. Interestingly, our theoretical results indicate a cavity-induced locking effect, which can be a complementary soliton trapping mechanism for the co-propagating solitons. Finally, these theoretical predications are experimentally verified, and we obtain both PRVS and LPS by adjusting the intracavity fiber birefringence.
由光纤双折射特性产生的矢量孤子的存在，对于锁模光纤激光器的稳定性越来越受到关注，特别是对于那些工作在高基频重复率 regime 的激光器，在该 regime 中，需要大量的光纤双折射来恢复正交偏振矢量孤子之间的相位关系，从而实现无偏振旋转的稳定锁模。这些矢量孤子可以表现出多样的随时间变化的偏振动力学，这阻碍了在高基频重复率下需要稳定且均匀脉冲序列的工业和科学应用。然而，这个紧迫的问题迄今为止很少被研究。为此，我们在这里从理论和实验上剖析了千兆赫兹重复率光纤激光器中矢量孤子的形成，并研究了抑制往返偏振动力学的有效方法。我们的数值模型可以通过改变光纤双折射量来预测高重复率锁模的动态和稳定 regime，分别产生偏振旋转矢量孤子（PRVS）和线偏振孤子（LPS）。通过使用解析方法进一步研究了这些动态行为。有趣的是，我们的理论结果表明了一种腔诱导锁定效应，这可以是共传播孤子的一种互补孤子俘获机制。最后，对这些理论预测进行了实验验证，并且我们通过调整腔内光纤双折射获得了 PRVS 和 LPS。
