Zou Jinhai, Kang Zhe, Wang Rui, Wang Hongjian, Liu Jiaxing, Dong Chuchu, Jiang Xiantao, Xu Bin, Cai Zhiping, Qin Guanshi, Zhang Han, Luo Zhengqian
Department of Electronic Engineering, Xiamen University, Xiamen 361005, China.
Nanoscale. 2019 Aug 29;11(34):15991-16000. doi: 10.1039/c9nr05096e.
Optical vortex beams are of tremendous interest in diverse applications for optical tweezers, high-resolution imaging, quantum information and optical communications. So far, these vortex laser sources largely rely on extra-cavity mode conversion by bulk optical elements (e.g. spatial light modulators, phase plates, etc.), resulting in a relatively poor purity, low conversion efficiency, non-compact structure and expensive package. Vortex beams generated directly from cavity-mode lasers is naturally an ideal solution, but almost all of them are not extended into the important visible spectral region. Here, we address the challenge through demonstrating, for the first time, visible-wavelength all-fiber pulsed vortex lasers. By using the fiber offset splicing technique and all-fiber visible resonators, 543.6 nm (green) and 634.7 nm (red) vortex beams are generated directly from Er3+: ZBLAN and Pr3+/Yb3+: ZBLAN fiber lasers with topological charges of ±1 and ±2, respectively. In particular, by exploiting an excellent visible-wavelength saturable absorber, visible-resonance-controlled gold nanorods, we further realize stable short-pulse operation of the 543.6 nm/634.7 nm vortex beams in the miniaturized visible fiber lasers. The green/red vortex laser pulses are ∼500 ns in duration, have a 40-400 kHz tunable repetition rate, and a >45 dB RF signal-to-noise ratio. This work may pave a path towards compact visible-wavelength pulsed vortex lasers for specific applications in STED microscopy and visible-light communications.
光学涡旋光束在光镊、高分辨率成像、量子信息和光通信等多种应用中备受关注。到目前为止，这些涡旋激光源在很大程度上依赖于由块状光学元件（如空间光调制器、相位板等）进行的腔外模式转换，这导致了相对较差的纯度、低转换效率、非紧凑结构和昂贵的封装。直接从腔模激光器产生的涡旋光束自然是一个理想的解决方案，但几乎所有这些光束都未扩展到重要的可见光谱区域。在此，我们首次通过展示可见波长全光纤脉冲涡旋激光器来应对这一挑战。通过使用光纤偏移熔接技术和全光纤可见谐振器，分别从拓扑电荷为±1和±2的Er3+:ZBLAN和Pr3+/Yb3+:ZBLAN光纤激光器中直接产生了543.6 nm（绿色）和634.7 nm（红色）的涡旋光束。特别是，通过利用一种出色的可见波长可饱和吸收体——可见共振控制的金纳米棒，我们在小型化可见光纤激光器中进一步实现了543.6 nm/634.7 nm涡旋光束的稳定短脉冲运行。绿色/红色涡旋激光脉冲的持续时间约为500 ns，具有40 - 400 kHz的可调重复频率，以及大于45 dB的射频信噪比。这项工作可能为在受激发射损耗显微镜和可见光通信等特定应用中实现紧凑的可见波长脉冲涡旋激光器铺平道路。
