Fibre lasers operating at the mid-IR have attracted enormous interest due to the plethora of applications in defence,security,medicine,and so on.However,no continuous-wave (CW) fibre lasers beyond 4 μm based on rare-earth-doped fibres have been demonstrated thus far.Here,we report efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time.By pumping with a self-developed thulium-doped fibre amplifier seeded by several diode lasers over the range of 1940-1983 nm,narrow linewidth mid-IR emission from 3810 to 4496 nm has been achieved with a maximum laser power of about 500 mW and a slope efficiency of approximately 18％.To the best of our knowledge,the wavelength of 4496 nm with strong absorption in silica-based fibres is the longest emission wavelength from a CW fibre laser,and the span of 686 nm is also the largest tuning range achieved to date for any CW fibre laser.By further reducing the HCF transmission loss,increasing the pump power,improving the coupling efficiency,and optimizing the fibre length together with the pressure,the laser efficiency and output power are expected to increase significantly.This work opens new opportunities for broadly tunable high-power mid-IR fibre lasers,especially beyond 4 μm.

Zhiyue Zhou;Zefeng Wang;Wei Huang;Yulong Cui;Hao Li;Meng Wang;Xiaoming Xi;Shoufei Gao;Yingying Wang

College of Advanced Interdisciplinary Studies,National University of Defense Technology,Changsha 410073,China;State Key Laboratory of Pulsed Power Laser Technology,Changsha 410073,China;Hunan Provincial Key Laboratory of High Energy Laser Technology,Changsha 410073,China;Institute of Photonics Technology,Jinan University,Guangzhou 511443,China

光：科学与应用（英文版）

[1]Zhiyue Zhou;Zefeng Wang;Wei Huang;Yulong Cui;Hao Li;Meng Wang;Xiaoming Xi;Shoufei Gao;Yingying Wang-.Towards high-power mid-IR light source tunable from 3.8 to 4.5 μm by HBr-filled hollow-core silica fibres)[J].光：科学与应用（英文版）,2022(01):101-113

HCFs

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