Active and passive coherent beam combining of thulium-doped fiber lasers

Pu Zhou; Xiaolin Wang; Yanxing Ma; Haotong Ma; Kai Han; Xiaojun Xu; Zejin Liu

doi:10.1117/12.870646

16 November 2010 Active and passive coherent beam combining of thulium-doped fiber lasers

Pu Zhou, Xiaolin Wang, Yanxing Ma, Haotong Ma, Kai Han, Xiaojun Xu, Zejin Liu

Proceedings Volume 7843, High-Power Lasers and Applications V; 784307 (2010) https://doi.org/10.1117/12.870646
Event: Photonics Asia 2010, 2010, Beijing, China

Abstract

Thulium-doped fiber laser (TFL), which emitted near 2 μm laser beam, has become the latest revolution in highpower fiber laser technology. Further increasing the output power will face great challenges induced by nonlinear effects; coherent beam combining of TFL can increase laser output power while simultaneously maintaining beam quality. In this manuscript, we will present our detailed investigation on coherent beam combining of TFLs. Three different approaches, i.e., interferometric array, mutual injection locking and active phasing based on multi-dithering technique, are employed. In the interferometric array scheme, coherent combining is realized by using an intracavity fiber coupler in an all-fiber laser array configuration. Efficient coherent combining can be achieved by providing sufficient loss discrimination. High combining efficiency of 85% for two fiber laser has been obtained. In mutual injection locking scheme, mutual coherence between the two fiber lasers is established by means of mutual coupling through two 3dB couplers. High combining efficiency of 99% for two fiber laser has been obtained, and the fringe contrast of the intensity pattern at the receiving plane is as high as 93%. In active phasing scheme, when the phase control system is in the closed loop, the fringe contrast of far-field intensity pattern is improved by more than 75 % from 10 % in open loop, and the residual phase error is less than λ/20.

Citation Download Citation

Pu Zhou, Xiaolin Wang, Yanxing Ma, Haotong Ma, Kai Han, Xiaojun Xu, and Zejin Liu "Active and passive coherent beam combining of thulium-doped fiber lasers", Proc. SPIE 7843, High-Power Lasers and Applications V, 784307 (16 November 2010); https://doi.org/10.1117/12.870646

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