Huang Maolin, Wu Jiadong, Hong Jiahao, Lei Hualei, Zhao Chujun, Chen Yu, Fan Dianyuan
Opt Express. 2021 Nov 22;29(24):40538-40546. doi: 10.1364/OE.442283.
High energy pulsed High-order Mode (HOM) beams has great potential in materials processing and particle acceleration. We experimentally demonstrate a high energy mode-locking Raman all-fiber laser with switchable HOM state. A home-made fiber mode-selective coupler (MSC) is used as the mode converter with a wide bandwidth of 60 nm. By combining advantages of MSC and stimulated Raman scattering, 1.1 μJ pulsed HOM beams directly emitting from the all-fiber cavity can be achieved. After controlling the category and phase delay of vector modal superposition, different pulsed HOM beams including cylindrical vector beams (CVBs) (radial and angular) and optical vortex beams (OVBs) are reasonably obtained with high purity (all over 95%), as well as arbitrary switching. Furtherly, the slope efficiency of HOM beams in the mode-locking and continuous wave operations are as much as 20.3% and 31.8%, respectively. It may provide an effective way to achieve high energy pulsed HOM beams.
高能量脉冲高阶模（HOM）光束在材料加工和粒子加速方面具有巨大潜力。我们通过实验展示了一种具有可切换HOM状态的高能量锁模拉曼全光纤激光器。使用自制的光纤模式选择耦合器（MSC）作为模式转换器，其带宽为60 nm。通过结合MSC和受激拉曼散射的优点，可以实现直接从全光纤腔发射的1.1 μJ脉冲HOM光束。在控制矢量模态叠加的类别和相位延迟后，可以合理地获得包括圆柱矢量光束（CVB）（径向和角向）和光学涡旋光束（OVB）在内的不同脉冲HOM光束，且纯度很高（均超过95%），并且可以任意切换。此外，HOM光束在锁模和连续波操作中的斜率效率分别高达20.3%和31.8%。这可能为实现高能量脉冲HOM光束提供一种有效方法。
