Gaussian-Shaped Gain-Dopant Distributed Fiber for High Output Power Fiber Amplifier

Zhilun Zhang,Nengli Dai,Gui Chen,Jinyan Li,Haiqing Li,Xianfeng Lin,Lei Liao,Yingbin Xing,Jinggang Peng

doi:10.1109/jphot.2021.3096716

Abstract

The remarkable evolution of ytterbium-doped fiber (YDF) lasers and amplifiers is interrupted by a limiting thermo-optical effect called transverse mode instability (TMI). Hereon, we propose a Gaussian-shaped gain-dopant distributed (GSGDD) YDF, which is fabricated by a modified chemical vapor deposition (MCVD) process combined with solution doping technique (SDT). By regulating the solution concentrations of soot layers, the content of Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions presents Gaussian-shaped distribution in the transverse direction while the refractive index profile (RIP) exhibits a stepped profile. The laser performance of this fiber is verified by a bidirectional pumped master oscillator power amplifier (MOPA). Over 3 kW near-single-mode laser output is obtained with the slope efficiency of 84.9%. At the highest power output, there are no Stokes light components in the spectrum and the beam quality M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> factor is ~1.45 These results suggest that the GSGDD fiber owns great potential to achieve high power output with excellent beam quality.

Highlights

Y B-DOPED fiber lasers have been widely applied to industrial processing, medical treatment, 3D printing, and military defense owing to the high conversion efficiency, efficient heat dissipation, compactness, and good beam quality [1]–[7]
We propose a Gaussian-shaped gain-dopant distributed (GSGDD) fiber fabricated by modified chemical vapor deposition (MCVD) process combined with solution doping technique (SDT) for the first time, whose core and inner cladding
The results showed that the time-domain signal was stable at the output power of 1598 W

Summary

Introduction

Y B-DOPED fiber lasers have been widely applied to industrial processing, medical treatment, 3D printing, and military defense owing to the high conversion efficiency, efficient heat dissipation, compactness, and good beam quality [1]–[7]. The output power of fiber lasers has been unprecedentedly improved, nonlinear effects such as stimulated Raman scattering (SRS) emerge when the peak power exceeds a certain threshold, leading to energy transfer to other wavelengths [1]. By enlarging the mode field area of the gain fiber, the SRS threshold is significantly improved. Since the TMI phenomenon was discovered in 2010, it has become the dominant limitation for further power scaling of Yb-doped fiber lasers. TMI appears when the output power exceeds a certain threshold, with beam profile transforming from a stable fundamental mode (FM) into an unsteady mode [9].

Methods

Results

Conclusion