Dang L, Zhang C, Zheng B, Cao Y, Huang L, Iroegbu PI, Lan T, Li J, Yin G, Zhu T. Tens of hertz ultra-narrow linewidth fiber ring laser based on external weak distributed feedback.
Opt Express 2022;
30:34575-34585. [PMID:
36242467 DOI:
10.1364/oe.470571]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 08/26/2022] [Indexed: 06/16/2023]
Abstract
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 Hz2/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.
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