Highly efficient all-fiber continuous-wave Raman graded-index fiber laser pumped by a fiber laser

Yao

et al. 2021

J. Lightwave Technol.

Raman fiber lasers (RFLs) are currently promising and versatile light sources for a variety of applications. So far, operations of high power and brightness-enhanced RFLs have absorbed enormous interests along with rapid progress. Nevertheless, the stable Raman lasing at high power levels remains challenged by the thermal effects. In an effort to realize more effective thermal management in high power RFLs, here we demonstrate, for the first time, an all-fiberized RFA employing metal-coated passive fiber enabling high power lasing. By employing aluminum to the cladding of graded-index (GRIN) passive fiber, the thermal abstraction of the laser devices is more sufficient to support low-temperature operation. The maximum output power reaches 3.083 kW at 1130 nm with a conversion efficiency of 78.7%. To the best of our knowledge, this is the first Raman laser generation based on metal-coated passive fiber. Meanwhile, it is also the highest power attained in the fields of all kinds of Raman lasers based on merely nonlinear gain.

Section: Introductionmentioning

confidence: 99%

3 kW Passive-Gain-Enabled Metalized Raman Fiber Amplifier With Brightness Enhancement

Yao

et al. 2021

J. Lightwave Technol.

“…The maximum power of LD-pumped GRIN RFL reached 62 W, and the M 2 was 3 with a BE of 25 [31] . Using the customized FBGs, the all-fiber GRIN RFL pumped by fiber lasers obtained 135 W power with an M 2 of 2.5 and a BE of 5.6 [32] . In general, the employment of FBGs written on GRIN fiber enabled all-fiber RFL with not only improved efficiency but also higher BE, with an M 2 improved to 2-3.…”

Section: Introductionmentioning

confidence: 99%

Greater than 2 kW all-passive fiber Raman amplifier with good beam quality

Yao

et al. 2020

High Pow Laser Sci Eng

We report a 2 kW all-fiberized Raman fiber amplifier with efficient brightness enhancement based on the graded-index fiber. The maximum power output reaches up to 2.034 kW centered at 1130 nm, with a conversion efficiency of 79.35% with respect to the injected pump power. To the best of our knowledge, this is the highest conversion efficiency obtained for any Raman laser system using graded-index fiber. An optimized fiber combiner adopting graded-index fiber as the pigtail fiber was fabricated, enabling the preservation of the seeding brightness in the core-pumped Raman fiber amplifier, and further enhancing the ultimate brightness of the output laser after amplification. At the maximum power output, the beam quality parameter M2 is 2.8, corresponding to a signal-to-pump brightness enhancement factor of 11.2. As far as we know, we obtain the highest brightness enhancement among Raman fiber lasers of over 100 W, and the best beam quality for graded-index Raman fiber lasers of over 150 W.

“…In 2017, A. Zlobina et al propose an all-fiber Raman fiber laser that also utilizes GRIN fiber and acquire power of 50 W at 954 nm, while the FBGs inscribed in GRIN fiber are the key devices which are specially fabricated for efficient reflection and mode selection effect [20]. In 2018 Y. Glick et al report an all-fiber Raman laser based on GRIN fiber and obtain power of 135 W at 1081 nm with brightness enhancement [21], and these achievements manifest that in pure RFLs the employment of GRIN fiber has potential in power scaling as well as brightness enhancement. It should be noted that the mentioned achievements are realized in oscillator configuration, which indicates that the handling and endurance ability of FBGs may be one of the restrictions for power scaling.…”

Section: Introductionmentioning

confidence: 99%

“…Then higher power output is acquired through fiber lasers employing integrated Yb-Raman gain [12][13][14], nevertheless the brightness decreases in the Raman shifting process and the issues of PD reappear which will influence the performance of laser system. Recently the fast development of fiber components and the brightness enhancement of pump lasers make it possible for power scaling in passive fibers that employ pure Raman gain [15][16][17][18][19][20][21][22]. For instance, using graded-index (GRIN) fiber in core-pumped structure has a relatively simple construction and enhances the brightness in fiber core.…”

Section: Introductionmentioning

confidence: 99%

Pure Passive Fiber Enabled Highly Efficient Raman Fiber Amplifier With Record Kilowatt Power

Leng

et al. 2019

IEEE Access

Kilowatt-level high efficiency all-fiberized Raman fiber amplifier based on pure passive fiber is proposed for the first time in this paper. The laser system is established on master oscillator power amplification configuration while a piece of graded-index passive fiber is utilized as stokes shifting as well as gain medium, which is entirely irrelevant to rare-earth-doped gain mechanism. When the pump power is 1368.8 W, we obtained 1002.3 W continuous-wave laser power at 1060 nm with the corresponding opticalto-optical efficiency of 84%. The beam parameter M 2 improves from 9.17 of the pump laser to 5.11 of the signal laser through the amplification process, and the brightness enhancement is about 2.57 at maximum output power as a consequence of the beam clean-up process in the graded-index fiber. To the best of our knowledge, we have demonstrated the first kilowatt-level high efficiency Raman fiber amplifier based on pure passive fiber with brightness enhancement.INDEX TERMS Fiber lasers, fiber nonlinear optics, high power amplifiers, Raman scattering.