Tens of hertz ultra-narrow linewidth fiber ring laser based on external weak distributed feedback

作者：Laiyang Dang, Chaoze Zhang, Bowen Zheng, Yulong Cao, Ligang Huang, Paul Ikechukwu Iroegbu, Tianyi Lan, Jiali Li, Guolu Yin, Tao Zhu · 发表于：Optics Express · 年份：2022 · DOI：10.1364/oe.470571 · 被引用次数：22 · 研究领域：Advanced Fiber Laser Technologies、Advanced Fiber Optic Sensors、Photonic Crystal and Fiber Optics

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 2 /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.