Sub-kHz high-order mode Brillouin random fiber laser based on long-period fiber grating and distributed Rayleigh scattering in a half-open linear cavity

Abstract

We demonstrate a narrow-linewidth high-order-mode (HOM) Brillouin random fiber laser (BRFL) based on a long-period fiber grating (LPFG) and distributed Rayleigh random feedback in a half-open linear cavity. The single-mode operation of the laser radiation with sub-kilohertz linewidth is achieved thanks to distributed Brillouin amplification and Rayleigh scattering along kilometer-long single mode fibers whilst a few mode fiber-based LPFGs enable the transverse mode conversion among a broadband wavelength range. Meanwhile, a dynamic fiber grating (DFG) is embedded and incorporated to manipulate and purify the random modes, which hence suppresses the frequency drift resulting from random mode hopping. Consequently, the random laser emission with either high-order scalar or vector modes can be generated with a high laser efficiency of 25.5% and an ultra-narrow 3-dB linewidth of 230 Hz. Furthermore, the dependence of the laser efficiency and frequency stability on the gain fiber length are also experimentally investigated. It is believed that our approach could provide a promising platform for a wide range of applications such as coherent optical communication, high-resolution imaging, highly sensitive sensing, etc.

Spectral Manipulations of Random Fiber Lasers: Principles, Characteristics, and Applications

“…Very recently, a narrow-linewidth high-order-mode BRFL was presented with the help of an LPFG, which is inscribed in FMF, SBS gain, and Rayleigh backscattering feedback. [177] As can be seen in Figure 10b, the 3 dB linewidth of the high-order-mode Brillouin random fiber lasing (the red curve in the inset) is as narrow as 230 Hz, even with the pump linewidth of 15.2 kHz (the purple curve in Figure 10b). In such a BRFL, the FMF-based LPFG enables the transverse mode conversion among a broad wavelength range.…”

“…Among all gain mediums of RFLs, the SBS process has unique merits, such as low threshold and narrow gain bandwidth, which favors developing RFLs with narrow linewidth. [16,21,22,165,[174][175][176][177] Figure 10. Narrow-linewidth radiation of RFLs.…”

“…Reproduced under the terms of the Optica Open Access Publishing Agreement. [177] Copyright 2023, Optica Publishing Group. c) Experimentally measured linewidth of the ERFL as a function of the high scattering fiber length.…”

A half-open cavity random fiber laser based on a single-mode fiber and fiber Bragg grating

“…Zhang et al designed a Brillouin RFL based on a long-period fiber grating in a half-open linear cavity. Distributed RS was realized by SMF [11]. Rybaltovsky et al reported a ytterbium-doped RFL using FBG array, and discussed different cavity lengths in the experiment.…”

Unveiling optical rogue wave behavior with temporally localized structures in Brillouin random fiber laser comb

“…Recently, RFLs have received a lot of attention due to their attractive features like low cost, simplicity of fabrication, and modeless lasing output. To date, RFLs based on a variety of gain mechanisms including rare-earth ion-doped fiber amplifiers, 16 stimulated Brillouin scattering (SBS), 17 stimulated Raman scattering, 18 , 19 and semiconductor optical amplifiers 20 have been reported. By employing regulating and control technologies combined with different gain mechanisms, performances of the reported RFLs have been well improved in many aspects, especially in their lower threshold, 21 higher output power, 22 wavelength tunability, 23 higher coherence, 24 narrower linewidth, 25 lower noise, 26 and more stabilized output power, 27 which enables a wide range of applications for RFLs in optical measurement, 28 microwave photonics, 29 optical fiber communication, 30 optical fiber sensing, 31 laser imaging, 32 and other fields 30 , 33 .…”