Research Progress of Ultra-Wide Tuned Random Raman Lasers in China

[Chinese instrument network instrument research and development] Recently, the research team led by Feng Yan, a researcher of the Space Laser Information Technology Research Center of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made new progress in the research of a random Raman fiber laser.

The figure shows the structure of an ultra-wide tuned random Raman laser
An ultra-wide tuned random Raman laser structure was proposed in the study, and a continuously tunable random Raman laser output of 1-1.9 μm was realized with a maximum output power of 6.2 W and an output wavelength of 1.82 μm.

The picture shows the 1-1.9μm continuously tunable random Raman laser output spectrum
In 2010, Sergei K. Turitsyn et al. reported on a new type of laser (Nature Photonics 4, 231-235 (2010)) that uses a standard single-mode fiber to provide Raman gains, providing distributed feedback through its backside Rayleigh scattering. Generate random laser output and formally put forward the concept of “randomly distributed feedback fiber laser”. Compared to conventional lasers, random lasers do not have resonant cavities with traditional meanings. Instead, they use a Rayleigh scattering effect in single-mode fibers to provide random distribution feedback to generate a novel non-cavity structured laser. Therefore, random-based feedback is used. Raman fiber laser has the advantages of simple structure, good directivity, continuous and stable output, and wavelength tunable. It has a wide range of potential applications in fields such as nonlinear optics, optical sensing and optical communication, biomedical imaging, and remote sensing.

In this study, the researchers combined the tunable properties of a random Raman laser with the cascaded properties. Through theoretical analysis and experimental studies, a tunable Erbium-doped fiber laser pumped random Raman laser was used to achieve ~50 nm tunable randomization. Laser output, combined with cascaded Raman technology to obtain a wideband tunable random laser output. A preliminary demonstration experiment using a standard single-mode fiber as a Raman gain fiber obtained a 300 nm continuous tunable random Raman laser output (Opt. Lett. 41, 215 (2016)), further wavelength tuning limited by four waves Spectral broadening effects caused by mixing. By optimizing the Raman gain fiber's dispersion, nonlinear coefficient, and transmission loss, while improving the output power of the tunable pump laser, a semi-open cavity random Raman laser is used to obtain a continuous tunable of 1-1.9 μm. With a random Raman laser output, the maximum output power is 6.2 W, and the corresponding output wavelength is 1.82 μm. This result was published in the "Scientific Report" (Sci. Rep. 7, 42611 (2017)).

The study was supported by the National Natural Science Foundation of China.

(Original title: Progress in the research of wide-tuned fiber lasers at Shanghai Optical Co., Ltd.)

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