Transverse mode coupling in monolithic few-mode fiber laser oscillators

Binyu Rao; Jinbao Chen; Zefeng Wang; Hao Li; Baolai Yang; Rong Zhao; Xinyu Ye; Hengyu Tang; Meng Wang; Zhixian Li; Zilun Chen; Jianqiu Cao; Hu Xiao; Wei Liu; Pengfei Ma; Tianfu Yao

doi:10.1038/s41377-025-01862-6

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Transverse mode coupling in monolithic few-mode fiber laser oscillators

Original Articles

- Transverse mode coupling in monolithic few-mode fiber laser oscillators
- Light: Science & Applications Vol. 14, Issue 7, Pages: 1965-1978(2025)
- Affiliations：
  
  1.College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
  2.Nanhu Laser Laboratory, National University of Defense Technology, Changsha, China
- Author bio：
  
  Jinbao Chen (kdchenjinbao@aliyun.com)
  Zefeng Wang (zefengwang_nudt@163.com)
  Baolai Yang (yangbaolai1989@163.com)
- Funds：
- DOI：10.1038/s41377-025-01862-6
  CLC：
- Received：31 December 2024，
  
  Revised：20 March 2025，
  
  Accepted：06 April 2025，
  
  Published Online：12 May 2025，
  
  Published：31 July 2025
- Accepted：
Scan QR Code
Rao, B. Y. et al. Transverse mode coupling in monolithic few-mode fiber laser oscillators. Light: Science & Applications, 14, 1965-1978 (2025).
DOI：

Rao, B. Y. et al. Transverse mode coupling in monolithic few-mode fiber laser oscillators. Light: Science & Applications, 14, 1965-1978 (2025). DOI： 10.1038/s41377-025-01862-6.

摘要

Abstract

Transverse mode instability (TMI)

induced by nonlinear thermal-optical coupling

poses a primary challenge for the power scaling of fiber lasers. In the fiber oscillator

a sealed resonant cavity

TMI could become particularly complex due to the mode competition during the laser oscillation. While traditional theories of TMI predominantly address two-mode coupling

this paper explores the TMI phenomena in few-mode fiber oscillators utilizing a holistic approach that includes solving steady-state thermal-optic coupling equations. The simulation shows that there is a non-monotonic correlation between bending loss and the TMI threshold

which is contrary to the monotonic associations suggested by two-mode interaction theory. When one high-order mode experiences net gain

fluctuations of the TMI threshold would occur

leading to the amplification of a new mode within the uncoupled frequency region

thus affecting the gain saturation. By designing the linewidth of a low-reflection grating (LR)

the modal power management in the uncoupled frequency domain can be achieved. An excessively broad LR linewidth exacerbates mode coupling within the shared frequency region

thus exacerbating TMI. To validate the theoretical simulation

we carefully fabricated LRs and optimized the fiber coiling to elevate the TMI threshold. Through careful optimization of LR linewidth and bending radii

we achieved a record-breaking laser output of 10.07 kW using a monolithic fiber oscillator

with no observable evidence of TMI. Our work demonstrates that modal power redistribution in independent frequency domains offers a novel approach to mitigating TMI in high-power fiber lasers. Additionally

it provides new insights into mode decoupling strategies pertinent to fiber communications.

关键词

Keywords

references

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