Recent research on nonlinear multimode interference (NL-MMI) based mode-locking method provides a new approach for ultrafast all-fiber lasers. Here, we report on the polarization dynamics of group velocity locked vector solitons (GVLVSs) and noise-like vector pulses (NLVPs) in a graded-index multimode fiber (GIMF) based all-fiber laser. Due to the non-polarization sensitive characteristic of the NL-MMI, emitted pulses automatically evolve into the vector multi-pulse complexes constituting two orthogonally polarized components. Beyond the traditional polarization resolved measurement, dispersive Fourier transform (DFT) and polarization beam splitting techniques are jointly adopted to enable insights into the transient polarization dynamics of the vector solitons. It is found in real time that the two orthogonally polarized components oppositely shift their central wavelengths to compensate the polarization dispersion. In addition, stationary and pulsating NLVPs are respectively unfolded by the DFT based polarization resolved measurement. Especially, the pulsating NLVPs before and after polarization resolved measurement are accompanied with the identical periodic spectral breathing process. All these findings reveal the vectorial nature in NL-MMI based ultrafast fiber lasers, as well as highlight the transient polarization dynamics and the long-term pulsation in dissipative systems.

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基于非线性多模干涉的超快光纤激光器的矢量性质

基于非线性多模干涉（NL-MMI）的锁模方法的最新研究为超快全光纤激光器提供了一种新方法。在这里，我们报告了基于渐变折射率多模光纤 (GIMF) 的全光纤激光器中群速度锁定矢量孤子 (GVLVS) 和类噪声矢量脉冲 (NLVP) 的偏振动力学。由于 NL-MMI 的非极化敏感特性，发射的脉冲会自动演变为构成两个正交极化分量的矢量多脉冲复合波。除了传统的偏振分辨测量外，还联合采用了色散傅立叶变换 (DFT) 和偏振分束技术，以深入了解矢量孤子的瞬态偏振动力学。实时发现两个正交偏振分量相反地移动它们的中心波长以补偿偏振色散。此外，静止和脉动 NLVP 分别通过基于 DFT 的偏振分辨测量展开。特别是，偏振分辨测量前后的脉动NLVP伴随着相同的周期性光谱呼吸过程。所有这些发现揭示了基于 NL-MMI 的超快光纤激光器的矢量性质，并突出了耗散系统中的瞬态偏振动力学和长期脉动。偏振分辨测量前后的脉动NLVP伴随着相同的周期性光谱呼吸过程。所有这些发现揭示了基于 NL-MMI 的超快光纤激光器的矢量性质，并突出了耗散系统中的瞬态偏振动力学和长期脉动。偏振分辨测量前后的脉动NLVP伴随着相同的周期性光谱呼吸过程。所有这些发现揭示了基于 NL-MMI 的超快光纤激光器的矢量性质，并突出了耗散系统中的瞬态偏振动力学和长期脉动。