Chinese Optics Letters, Vol. 17, Issue 12, 120602 (2019)
Ultra-broadband highly efficient mode converter at 1 μm fabricated by a line-focused CO2 laser
Xin Tian1,2,3, Hao Li1,2,3, Le Liu1,2,3, Meng Wang1,2,3, Xiaoming Xi1,2,3, and Zefeng Wang1,2,3,*
- 1College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
- 2State Key Laboratory of Pulsed Power Laser Technology, Changsha 410073, China
- 3Hunan Provincial Key Laboratory of High Energy Laser Technology, Changsha 410073, China
We report here an ultra-broadband linearly polarized (LP) LP01 LP11 mode converter operating at 1 μm based on a long period fiber grating (LPFG) fabricated in a conventional two-mode fiber (TMF) by a line-focused CO2 laser. The measured 3 dB bandwidth is about 240 nm, which is the broadest bandwidth for such fiber mode converters. The maximum conversion efficiency between the LP01 and LP11 modes is >99% over the range of 1000 nm to 1085 nm, almost covering the whole emission band of Yb3+, which is useful for further power scaling of high-power fiber lasers operating at the 1 μm band.