Brillouin gain spectrum characterization in Ge-doped large-mode-area fibers

The dependence of Brillouin gain spectrum (BGS) characteristics, including the Brillouin frequency shift (BFS) and the BGS bandwidth, on germanium concentration in large-mode-area Ge-doped passive fibers is investigated theoretically and experimentally. The simulation results show that the BFS is inversely proportional to GeO₂ concentration, and the BGS bandwidth initially increases with the augment of GeO₂ concentration, and then decreases. The BGSs of four fibers with core diameters of 10 μm and 20 μm for different GeO₂ concentrations are compared experimentally. Experimental results demonstrate that with the same core diameter, the variations of BFS and BGS bandwidths with GeO₂ concentration accord with the simulation results. Additionally, the BGS characteristics of three large-mode-area passive fibers with diameters of 10 μm, 25 μm, and 30 μm are measured, which confirm that the increasing of the fiber diameters will cause the BGS bandwidth to broaden. We believe that these results can provide valuable references for modulating the high-power narrow-linewidth fiber lasers and Brillouin fiber amplifiers.     

国产25/400μm掺镱双包层光纤实现2.2kW窄线宽单模激光输出

基于自主研制的均匀掺杂低热光系数25/400μm掺镱双包层光纤,开展了全光纤高功率窄线宽光纤激光放大实验。激光系统实现了中心波长为1060.3 nm、线宽为25 GHz、最高功率为2.2 kW的单模激光输出,其斜率效率达78%,光束质量因子M~2≈1.2,其功率是目前报道的基于国产25/400μm掺镱双包层光纤窄线宽放大器单模激光输出的最高功率。