• Chinese Journal of Lasers
  • Vol. 48, Issue 20, 2000001 (2021)
Pu Zhou*, Jinyong Leng, Hu Xiao, Pengfei Ma, Jiangming Xu, Wei Liu, Tianfu Yao, Hanwei Zhang, Liangjin Huang, and Zhiyong Pan
Author Affiliations
  • College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, Hunan 410073, China
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    DOI: 10.3788/CJL202148.2000001 Cite this Article Set citation alerts
    Pu Zhou, Jinyong Leng, Hu Xiao, Pengfei Ma, Jiangming Xu, Wei Liu, Tianfu Yao, Hanwei Zhang, Liangjin Huang, Zhiyong Pan. High Average Power Fiber Lasers: Research Progress and Future Prospect[J]. Chinese Journal of Lasers, 2021, 48(20): 2000001 Copy Citation Text show less

    Abstract

    Significance High-average-power fiber lasers have many important applications in advanced manufacturing, energy exploration, and national security benefit from the advantages of compact structure, high electro-optical efficiency, and flexible operation. In 2009 and 2010, IPG Photonics demonstrated a single-fiber single-mode laser with an output power of 9.6 kW and 10.5 kW, respectively, two important milestones in the field of fiber lasers. In the past 10 years (2010--2020), high-average-power fiber lasers and systems of various operation bands have developed rapidly and moved towards large-scale applications. In this paper, the research progress of high-average-power fiber laser technology in the past decade is reviewed.

    Progress Firstly, the realization history and parameter analysis of 10 kW single-mode fiber laser are given, and the important characteristics of 10 kW single-mode fiber laser is summarized. Specifically, the first one is the tandem-pump technology, the second one is the amplifier structure, the third one is ytterbium ion as the gain medium of the amplifier stage, the fourth one is that the relatively moderate laser output linewidth, and the fifth one is continuous wave operation.

    Second, the pump technology of high-average-power fiber lasers shifts from single to multiple. The pump source is one of the most critical and costly components in a high-average-power fiber laser system. With the development of semiconductor laser technology and double-clad fiber laser technology, semiconductor laser and ytterbium-doped double-clad fiber are once more the essential configurations in a high-average-power fiber laser system. For a period of time, the brightness of semiconductor lasers is unable to meet the development of high-average-power fiber lasers, so researchers begin to introduce new solutions such as tandem-pump technology. In recent years, with the rapid increase in the brightness of semiconductor lasers and the continuous discovery of new scientific issues, the pumping technology of high-average-power fiber lasers has gradually diversified, which has promoted the development of fiber laser technology.

    Third, the system structure of high-average-power fiber lasers expands from the amplifier structure to the resonant cavity structure and cavity-free structure. In recent years, with the development of passive devices and semiconductor lasers, the output power of fiber lasers with resonant cavity structures has increased rapidly. In addition, new concepts such as fiber lasers without cavity structures have also been proposed and quickly realized. The high-average-power fiber laser system structure has entered a stage in which various system structures develop parallelly.

    Fourth, the operation wavelength of high-average-power fiber lasers begins to expand from a short wavelength region to a long wavelength region, and from visible lasers to mid-infrared lasers. Although the radiation spectrum of ytterbium-doped fibers covers 0.96 μm to 1.2 μm, the net gain of the sidebands is relatively small and it is difficult to achieve a high-average-power output directly. Due to the traction of important applications, significant results have been achieved in the above fields. In addition, other new gain media including doped fibers and passive fibers have also been applied to realize a high-average-power output, which enables the operation wavelength of high-average-power fiber lasers to cover from shortwave to longwave, and from visible to mid-infrared.

    Fifth, the laser linewidth of high-average-power fiber lasers could cover from ultra-narrow linewidth to supercontinuum regions, and high-average-power pulsed fiber lasers have also been realized. The limiting factors for high-average-power fiber lasers with different laser linewidths are different. As for the single-frequency fiber lasers and narrow-linewidth fiber lasers, the stimulated Brillouin scattering (SBS) effect is one of the main issues in the power scaling. As for the broadband fiber lasers, the stimulated Raman scattering (SRS) effect is one of the main issues in the power scaling. In addition, the newly discovered mode instability (MI) effect becomes a technical bottleneck in the power scaling of high-average-power fiber lasers, which has also shown an obvious correlation with laser linewidth. Due to the high peak power of pulsed lasers, the nonlinear effects are more critical in high-average-power pulsed fiber lasers. Therefore, there still exists a gap in magnitude between the highest average power of pulsed fiber lasers and the highest average power of continuous-wave fiber lasers.

    Prospects In future work, the high-average-power fiber laser technology is moving toward the stage of controllable, which is specifically manifested in three areas. The first one is the controllable pulse characteristics, including repetition rate, pulse width, and waveform. Researchers have achieved an early control of repetition rate and pulse width of high-power fiber lasers. The second one is the controllable spectral characteristics, including center wavelength, linewidth, and spectral shape. With the continuous discovery of phenomena such as the influence of spectral characteristics on nonlinear effects, the ability of scientific researchers to control the spectral characteristics of high-average-power fiber lasers is continuously enhanced. The third one is the controllable spatial-mode characteristics. Mode-controllable high-average-power fiber lasers are currently a hotspot in the advanced manufacturing, which may bring important technological innovations.

    Pu Zhou, Jinyong Leng, Hu Xiao, Pengfei Ma, Jiangming Xu, Wei Liu, Tianfu Yao, Hanwei Zhang, Liangjin Huang, Zhiyong Pan. High Average Power Fiber Lasers: Research Progress and Future Prospect[J]. Chinese Journal of Lasers, 2021, 48(20): 2000001
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