The random distributed-feedback Raman fiber laser (RRFL) is a new approach to obtain a high-power laser. In this Letter, we report a RRFL with quasi-kilowatt output power for the first time based on a half-open cavity. It consists of a piece of a large-mode-area passive fiber with a core diameter of 20 μm and a high-reflectivity fiber Bragg grating (FBG). By optimizing the fiber length to be 90 m, a 919 W random laser at 1150 nm is achieved in the forward output end. Due to the nonlinear Kerr-effect-induced spectral broadening, the spectrum of the generated random laser exceeds the bandwidth of the FBG, resulting in a 66 W random laser emitting from the backward direction at the maximum power. To the best of our knowledge, it is the first quasi-kilowatt random fiber laser, and it is also the highest power reported of a 1150 nm laser. This work provides a rather simple structure to obtain a kilowatt-level, stable random laser output.

In this work, an all-fiberized and narrow-linewidth fiber amplifier with record output power and near-diffraction-limited beam quality is presented. Up to 6.12 kW fiber laser with the conversion efficiency of approximately 78.8% is achieved through the fiber amplifier based on a conventional step-index active fiber. At the maximum output power, the 3 dB spectral linewidth is approximately 0.86 nm and the beam quality factor is M _x ² = 1.43, M _y ² = 1.36. We have also measured and compared the output properties of the fiber amplifier employing different pumping schemes. Notably, the practical power limit of the fiber amplifier could be estimated through the maximum output powers of the fiber amplifier employing unidirectional pumping schemes. Overall, this work could provide a good reference for the optimal design and potential exploration of high-power narrow-linewidth fiber laser systems.

We demonstrate a tunable, high order cascaded random Raman fiber laser (RRFL) with high purity at 1.7 µm band by using a high power amplified spontaneous emission source (ASE) with both wavelength and linewidth tunability as pump source. The influence of the spectral bandwidth of the ASE source on the spectral purity of the output at 1.7 µm band is investigated. By adjusting the spectral bandwidth of the ASE source to the optimized 20 nm, output power >14 W with spectral purity up to 98.29% at 1715 nm is achieved. As far as we know, this is the highest spectral purity ever reported for a RRFL at 1.7 µm region. Furthermore, by adjusting the central wavelength of ASE source, the output of the RRFL can be tuned from 1695 to 1725 nm with >10 W output power. What’s more, the spectral purity is above 92% over a tuning range from 1705 to 1725 nm.

In this work, we conduct a detailed experimental study on the impact of signal bandwidth on the TMI threshold of fiber amplifiers. Both the filtered superfluorescent fiber sources and the phase-modulated single-frequency lasers are employed to construct seed lasers with different 3 dB spectral linewidths ranging from 0.19 nm to 7.97 nm. The TMI threshold of the fiber amplifier employing those seed lasers are estimated through the intensity evolution of the signal laser, and different criteria have been utilized to characterize the spectral linewidth of the seed lasers. Notably, the experimental results reveal that the TMI threshold of fiber amplifiers grows, keeps constant, and further grows as a function of spectral linewidth of seed lasers. Our experimental results could provide a well reference to understand the mechanism of the TMI effect and optimize the TMI effect in high-power fiber amplifiers.

The famous demonstration of optical rogue waves (RWs), a powerful tool to reveal the fundamental physics in different laser scenarios, opened a flourishing time for temporal statistics. Random fiber laser (RFL) has likewise attracted wide attention due to its great potential in multidisciplinary demonstrations and promising applications. However, owing to the distinctive cavity-free structure, it is a scientific challenge to achieve temporal localized RWs in RFLs, whose feedback arises from multiple scattering in disordered medium. Here, we report the exploration of RW in the highly skewed, transient intensity of an incoherently pumped RFL for the first time, to our knowledge, and unfold the involved kinetics successfully. The corresponding frequency domain measurements demonstrate that the RW event arises from a crucial sustained stimulated Brillouin scattering process with intrinsic stochastic nature. This investigation highlights a novel path to fully understanding the complex physics, such as photon propagation and localization, in disordered media.

Multiwavelength fiber lasers, especially those operating at optical communication wavebands such as 1.3 μm and 1.5 μm wavebands, have huge demands in wavelength division multiplexing communications. In the past decade, multiwavelength fiber lasers operating at 1.5 μm waveband have been widely reported. Nevertheless, 1.3 μm waveband multiwavelength fiber laser is rarely studied due to the lack of proper gain mechanism. Random fiber laser (RFL), owing to its good temporal stability and flexible wavelength tunability, is a great candidate for multiwavelength generation. Here, we reported high power multiwavelength generation at 1.3 μm waveband in RFL for the first time. At first, we employed a section of 10 km G655C fiber to provide Raman gains, as a result of which, 1.07 W multiwavelength generation at 1.3 μm waveband with an optical to signal noise ratio of ∼33 dB is demonstrated. By tuning the pump wavelength from 1055 nm to 1070 nm, tunable multiwavelength output covering the range of 1300-1330 nm can be achieved. Furtherly, we realized 4.67 W multiwavelength generation at 1.3 μm waveband by shortening the fiber length to 4 km. To the best of our knowledge, this is the highest output power ever reported for multiwavelength fiber lasers.