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中国物理学会期刊

百兆赫兹重频的轨道角动量模式飞秒光纤激光器

CSTR: 32037.14.aps.73.20231085

Orbital angular momentum mode femtosecond fiber laser with over 100 MHz repetition rate

CSTR: 32037.14.aps.73.20231085
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  • 轨道角动量(orbital angular momentum, OAM)模式激光器在大容量通信系统、激光加工、微粒子操作、量子光学领域研究有潜在应用价值. OAM模式飞秒光纤激光器具有结构简单、成本低、峰值功率高等优势而被重点研究. 当前OAM模式飞秒光纤激光器在重复频率、脉冲宽度、光谱宽度等关键参数上分别都有突破, 但性能难以兼得, 且重复频率目前在数十MHz. 本文基于模式相位匹配原理, 制作了大带宽的模式耦合器, 结合非线性偏振旋转锁模机理, 通过优化腔内的色散, 搭建了百兆赫兹重复频率的OAM模式飞秒光纤激光器. 实验结果表明, 一阶OAM模式光纤激光器的重复频率可达113.6 MHz, 脉冲半高全宽98 fs, 10 dB带宽可达101 nm; 二阶OAM模式光纤激光器的重复频率可达114.9 MHz, 脉冲半高全宽60 fs, 10 dB带宽可达100 nm. 相对于已报道的方案, 本文报道的方案在重复频率、脉宽和光谱宽度等关键参数上综合性能较好, 有望更广泛地应用于OAM通信、粒子操控等研究领域.

     

    Orbital angular momentum (OAM) lasers have potential applications in large capacity communication systems, laser processing, particle manipulation and quantum optics. OAM mode femtosecond fiber laser has become the research focus due to the advantages of simple structure, low cost and high peak power. At present, OAM mode femtosecond fiber lasers have made some breakthroughs in key parameters such as repetition frequency, pulse width, spectrum width, but it is difficult to achieve good overall performance. Besides, the repetition rate is tens of MHz at present. In this paper, a large-bandwidth mode coupler is made based on the mode phase matching principle. In coupler, the first order mode coupler with 3 dB polarization dependent loss is made by the technology of strong fused biconical taper, and the second order mode coupler with 0.3 dB polarization dependent loss is made by the technology of weak fused biconical taper. By combining the nonlinear polarization rotation mode-locking mechanism, OAM mode femtosecond fiber laser with over 100 MHz repetition rate is built. The achievement of the key parameters is attributed to the selection of dispersion shifted fibers that can accurately adjust intracavity dispersion. Comparing with traditional dispersion compensation fibers (DCF), the group velocity dispersion is reduced by an order of magnitude, so it can better adjust intracavity dispersion to achieve the indexes of large spectral bandwidth and narrow pulse width. In addition, the diameter of the fiber is 8 μm, which is the same as that of a single mode fiber. Comparing with DCF, the fusion loss can be ignored, so only a shorter gain Erbium-doped fiber is required, which ensures a shorter overall cavity length and achieves high repetition frequency. The experimental results show that the first order OAM mode fiber laser has 113.6 MHz repetition rate, 98 fs half-height full pulse width, and 101 nm 10 dB bandwidth. Second-order OAM mode fiber laser has 114.9 MHz repetition rate, 60 fs half-height full pulse width, and 100 nm 10 dB bandwidth. Compared with the reported schemes, our scheme has good performance in key parameters such as repetition rate, pulse width and spectral width. We believe that the OAM mode fiber laser with excellent performance is expected to be widely used in OAM communication, particle manipulation and other research fields.

     

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