We report the result of achieving a random fiber laser (RFL) with record 200-W-level power output. The highest output power is realized by a simple 120 m long cavity at a working wavelength of 1173 nm while pumping at 1120 nm. The maximum observed optical-to-optical efficiency reaches $\sim 89\%$, which is believed to be the highest value ever reported for RFLs. In addition, numerical calculations on different order Raman Stokes wave thresholds based on the theoretical model are carried out for comparison with the experimental data. The presented work effectively advances the power scalability, and the numerical model well describes the lasing thresholds in such short cavity RFLs.

The transverse mode instability (TMI) has been one of the main limitations for the power scaling of single mode fiber lasers. In this work, we report a 6 kW single mode monolithic fiber laser enabled by effective mitigation of the TMI. The fiber laser employs a custom-made wavelength-stabilized 981 nm pump source, which remarkably enhanced the TMI threshold compared with the wavelength of 976 nm. With appropriately distributing bidirectional pump power, the monolithic fiber laser is scaled to 6 kW with single mode beam quality (M²<1.3). The stability is verified in a continuous operation for over 2 hours with power fluctuation below 1%.

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.

A fiber laser based on random distributed feedback has attracted increasing attention in recent years, as it has become an important photonic device and has found wide applications in fiber communications or sensing. In this article, recent advances in high‐power random distributed feedback fiber laser are reviewed, including the theoretical analyses, experimental approaches, discussion on the practical applications and outlook. It is found that a random distributed feedback fiber laser can not only act as an information photonics device, but also has the feasibility for high‐efficiency/high‐power generation, which makes it competitive with conventional high‐power laser sources. In addition, high‐power random distributed feedback fiber laser has been successfully applied for midinfrared lasing, frequency doubling to the visible and high‐quality imaging. It is believed that the high‐power random distributed feedback fiber laser could become a promising light source with simple and economic configurations. image

We report on the demonstration of a high power, high beam quality random fiber laser. It is a half-open cavity based on 130-m-long large mode area step-index fiber with a core diameter of 20 μm and a numerical aperture of 0.08. The random laser cavity, whose central wavelength is 1120 nm, is pumped by a 1070 nm Yb-doped fiber oscillator. The maximum output power is 418 W with respect to the injected pump power of 588 W, corresponding to the optical-to-optical efficiency of 71%. The output power, spectral, and temporal characteristics are carefully presented and discussed, showing that such a cavity can export high power random laser stably and effectively. The far field beam quality is also measured, and the profile is nearly a Gaussian shape. This work provides an impactful method to advance the output power of random fiber lasers.

We report a high-power high-efficiency single-mode all-fiber Raman fiber laser (RFL) operating at 1173 nm. With the core pumped by a 144-W 1120-nm Yb-doped fiber laser, an output power of 119 W at a wavelength of 1173 nm was obtained, corresponding to an optical efficiency of 82%. To the best of our knowledge, it is the highest power at the 1150-1200-nm laser band by using common silica fiber. The optical efficiency of the RFL with high output coupler (OC) reflectivity and short fiber length is discussed. We also carefully measured the output Raman spectrums under different cavity parameters and presented primary analysis. The results show that the bandwidth increases near linearly with laser output power, rather than a square-root law concluded for high Q-value and long-cavity RFLs in previous published literatures. Increasing the length of the gain fiber and the reflectivity of the OC would also broaden the output spectral bandwidth.