Yimin Zhang, Tao Runxia, Li Hongxun, Fang Wentan, Dong Zhipeng, Dai Chuansheng, Xu Lixin, Gu Chun, Chen Wei, Zhu Yonggang, Zhan Qiwen, Yao Peijun
Opt Express. 2020 Jun 8;28(12):18351-18359. doi: 10.1364/OE.395757.
An all-fiber laser using polarization-maintaining and ring-core fibers that are capable of automatically generating stable TE and TM modes is proposed and demonstrated experimentally. Two vector-mode coupling long-period fiber gratings (LPFGs) fabricated by a high-frequency CO laser are used in the fiber laser to realize efficient coupling between HE mode and TE/TM mode. The polarization dependence of the LPFGs is simulated using the coupled-mode theory and verified by experiments. A ring-core fiber is employed to support the stable propagation of TE and TM modes. By carefully aligning the polarization direction of the input light, the mode coupling ratios of both LPFGs exceed 15 dB. The mode purities of TE and TM modes are 92.4% and 97.3%, respectively. Owing to the all-polarization-maintaining structure, the laser output is highly stable under environmental disturbance. This laser can be used as a stable cylindrical vector beam source for a wide range of applications, including surface plasmon excitation, optical tweezers, high-resolution metrology and so on.
提出了一种采用保偏光纤和环形芯光纤的全光纤激光器，该激光器能够自动产生稳定的TE和TM模式，并进行了实验验证。光纤激光器中使用了两个由高频CO激光器制造的矢量模式耦合长周期光纤光栅（LPFG），以实现HE模式与TE/TM模式之间的高效耦合。利用耦合模理论对LPFG的偏振依赖性进行了模拟，并通过实验进行了验证。采用环形芯光纤来支持TE和TM模式的稳定传播。通过仔细调整输入光的偏振方向，两个LPFG的模式耦合比均超过15 dB。TE和TM模式的模式纯度分别为92.4%和97.3%。由于全保偏结构，激光输出在环境干扰下高度稳定。这种激光器可作为稳定的圆柱矢量光束源，用于包括表面等离子体激发、光镊、高分辨率计量等广泛的应用。
