Low-Threshold and Sub-kHz-Linewidth Brillouin Laser Based on Chalcogenide Fiber at 2 \mum

• Published in: Journal of lightwave technology 2022-11, Vol.40 (22), p.7390-7395
• Main Authors: Wang, Yingying, Yang, Lingling, Yang, Fan, Xu, Lulu, Wu, Zhongchao, Liu, Teng, Wu, Duanduan, Zhang, Lei, Dai, Shixun
• Format: Article
• Language: English
• Subjects: Fiber lasers; nonlinear optics; Optical fiber amplifiers; Optical fiber couplers; Optical fiber devices; Optical fiber polarization; Optical fibers; Scattering; stimulated Brillouin scattering
• ISSN: 0733-8724
• DOI: 10.1109/JLT.2022.3200700

We experimentally demonstrate a Brillouin fiber laser (BFL) with a low threshold and narrow linewidth at 2 \mum employing a chalcogenide As_{2}S_{3} fiber as the Brillouin gain fiber. The As_{2}S_{3} fiber exhibits a Brillouin gain coefficient of 1.76\times 10^{-9} m/W at 2 \mum, which is two orders of magnitude higher than that of the silica fiber, together with a Brillouin frequency shift of 6.308 GHz and a gain linewidth of 10.2 MHz. By theoretically optimizing the fiber length adopted in the Brillouin ring cavity, a 3-m-long segment of the As_{2}S_{3} fiber is used to realize a BFL with excellent performance in terms of laser power threshold and linewidth. The BFL shows a total cavity loss of 6.18 dB, corresponding to a cavity feedback parameter of 24.1\%. The lowest laser power threshold of 39 mW and narrowest laser linewidth of \sim619 Hz so far, to the best of our knowledge, are simultaneously achieved for the BFL at 2 \mum. These results benefit from not only the extremely high Brillouin gain coefficient and small effective mode field area of the As_{2}S_{3} fiber but also a suitable Brillouin gain fiber length and low cavity loss of the BFL. The relative intensity noise and temporal stability of the BFL are also investigated. Such a low-threshold and sub-kHz-linewidth laser will facilitate the development of practical applications such as gas sensing and coherent LIDAR in the 2 \mum spectral range.