Dang Laiyang, Zhang Chaoze, Zheng Bowen, Cao Yulong, Huang Ligang, Iroegbu Paul Ikechukwu, Lan Tianyi, Li Jiali, Yin Guolu, Zhu Tao
Opt Express. 2022 Sep 12;30(19):34575-34585. doi: 10.1364/OE.470571.
We suggest and demonstrate a single-frequency fiber ring laser with an ultra-narrow linewidth based on an external weak distributed feedback. A π phase-shifted fiber Bragg grating (PSFBG) is used to improve mode selection and enable single-longitudinal mode (SLM) laser operation. The linewidth is then further strongly compressed using a signal generated by a weak distributed feedback structure (WDFS) and injected into the main laser cavity to suppress spontaneous emission. The resulting ultra-narrow linewidth fiber ring laser achieves a side-mode suppression ratio (SMSR) of ∼72 dB, and low white frequency noise of ∼10.3 Hz/Hz, which correspond to an instantaneous linewidth of ∼32.3 Hz in the normal operating condition of the laser. Our linewidth compression mechanism not only solves the problems associated with deep linewidth compression in long-cavity fiber laser, but also fosters the development of practical and reliable all-fiber structures. Our laser source is characterized by low cost, high coherence, and low noise, which are highly desirable features in coherent optical detection, high-resolution spectrometers, microwave photonics, and optical sensing.
我们提出并展示了一种基于外部弱分布反馈的具有超窄线宽的单频光纤环形激光器。采用π相移光纤布拉格光栅（PSFBG）来改善模式选择并实现单纵模（SLM）激光运转。然后，利用由弱分布反馈结构（WDFS）产生并注入主激光腔的信号来进一步强烈压缩线宽，以抑制自发辐射。所得的超窄线宽光纤环形激光器实现了约72 dB的边模抑制比（SMSR）和约10.3 Hz/Hz的低白频噪声，这对应于激光器正常工作条件下约32.3 Hz的瞬时线宽。我们的线宽压缩机制不仅解决了与长腔光纤激光器中深线宽压缩相关的问题，还促进了实用且可靠的全光纤结构的发展。我们的激光源具有低成本、高相干性和低噪声的特点，这些都是相干光探测、高分辨率光谱仪、微波光子学和光学传感中非常理想的特性。
