Temporal frequency study on stimulated Raman scattering induced mode instability in high power fiber lasers

Qiang Shu; Qiuhui Chu; Rumao Tao; Chao Guo; Honghuan Lin; Jianjun Wang

doi:10.1117/12.2565359

17 April 2020 Temporal frequency study on stimulated Raman scattering induced mode instability in high power fiber lasers

Qiang Shu, Qiuhui Chu, Rumao Tao, Chao Guo, Honghuan Lin, Jianjun Wang

Author Affiliations +

Proceedings Volume 11455, Sixth Symposium on Novel Optoelectronic Detection Technology and Applications; 114557N (2020) https://doi.org/10.1117/12.2565359
Event: Sixth Symposium on Novel Photoelectronic Detection Technology and Application, 2019, Beijing, China

Abstract

In this paper, we report the experimental study on stimulated Raman scattering (SRS) induced mode instabilities (MI) in large mode area step-index fiber in a counter-pumped all-fiberlized amplifier. When the output power is scaled to 1560W, the ratio of SRS is 2% and the beam quality factor M2 is about 1.4. With the further scaling of output power, the SRS power begins to increase nonlinearly, and then the beam quality degrades obviously when the ratio of SRS exceeds 3%, and the M2 is about 2.1 at 1910W, that is the SRS induced MI. The phenomenon is accompanied by the temperature increasing of output passive fiber, which is caused by heat deposition of quantum defect between signal light and Raman light. The temporal dynamics of SRS induced MI is studied in detail for the first time, which are characterized by using both camera measurement and photodiode traces. The experiment results express that both the output power and output beam profile remain stable before the MI occurs, and fluctuate obviously after the onset of SRS induced MI. The temporal frequency investigation indicates that the SRS induced MI is a dynamic process with slow speed fluctuation at second level, and the Fourier spectrum of time trace is within 10Hz, and the SRS induced mode degradation is different from the Yb-gain induced MI effect.

Citation Download Citation

Qiang Shu, Qiuhui Chu, Rumao Tao, Chao Guo, Honghuan Lin, and Jianjun Wang "Temporal frequency study on stimulated Raman scattering induced mode instability in high power fiber lasers", Proc. SPIE 11455, Sixth Symposium on Novel Optoelectronic Detection Technology and Applications, 114557N (17 April 2020); https://doi.org/10.1117/12.2565359

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KEYWORDS

Amplifiers

Fiber lasers

Raman scattering

High power fiber lasers

Fiber amplifiers

Step index fibers

Temperature metrology

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