A kind of tapered segmented cladding fiber (T-SCF) with large mode area (LMA) is proposed, and the mode and amplification characteristics of T-SCFs with concave, linear, and convex tapered structures are investigated based on finite-element method (FEM) and few-mode steady-state rate equation. Simulation results indicate that the concave tapered structure can introduce high loss for high-order modes (HOMs) that is advantageous to achieve single-mode operation, whereas the convex tapered structure provides large effective mode area that can help to mitigate nonlinear effects. Meanwhile, the small-to-large amplification scheme shows further advantages on stripping off HOMs, and the large-to-small amplification scheme decreases the heat load density induced by the high-power pump. Moreover, single-mode propagation performance, effective mode area, and heat load density of the T-SCF are superior to those of tapered step index fiber (T-SIF). These theoretical model and numerical results can provide instructive suggestions for designing high-power fiber lasers and amplifiers.

中文翻译：

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大模面积有源锥形分段包层光纤的放大特性

提出了一种具有大模面积（LMA）的锥形分段包层光纤（T-SCF），并基于有限元方法研究了具有凹、线性和凸锥形结构的T-SCF的模式和放大特性。 FEM) 和少模态稳态速率方程。仿真结果表明，凹锥形结构可以为高阶模式（HOM）引入高损耗，有利于实现单模操作，而凸锥形结构提供大的有效模式面积，有助于减轻非线性效应。同时，小到大放大方案在剥离HOM方面表现出进一步的优势，大到小放大方案降低了大功率泵引起的热负荷密度。此外，单模传播性能、有效模式面积、T-SCF 的热负荷密度和热负荷密度均优于锥形阶梯折射率光纤 (T-SIF)。这些理论模型和数值结果可为设计高功率光纤激光器和放大器提供指导性建议。