• High Power Laser Science and Engineering
  • Vol. 9, Issue 2, 02000e32 (2021)
Caijian Xie1、*, Tigang Ning1, Jingjing Zheng1, Li Pei1, Jianshuai Wang1, Jing Li1, Haidong You2, Chuangye Wang1, and Xuekai Gao1
Author Affiliations
  • 1Key Laboratory of All Optical Network & Advanced Telecommunication Network of EMC, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing100044, China
  • 2Science and Information College, Qingdao Agricultural University, Qingdao266109, China
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    DOI: 10.1017/hpl.2021.20 Cite this Article Set citation alerts
    Caijian Xie, Tigang Ning, Jingjing Zheng, Li Pei, Jianshuai Wang, Jing Li, Haidong You, Chuangye Wang, Xuekai Gao. Amplification characteristics in active tapered segmented cladding fiber with large mode area[J]. High Power Laser Science and Engineering, 2021, 9(2): 02000e32 Copy Citation Text show less

    Abstract

    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.
    $$\begin{align}\rho (z)=\frac{b_0-{b}_{\mathrm{f}}}{2L}{z}^2+\frac{b_{\mathrm{f}}}{2}z+\frac{1}{2}{D}_1,\end{align}$$((1))

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    $$\begin{align}{n}_{\mathrm{bent}}\left(x,y,z\right)={n}_{\mathrm{straight}}\left(x,y,z\right)\left(1+\frac{\overrightarrow{x}\cos \varphi +\overrightarrow{y}\sin \varphi }{\rho R}\right),\end{align}$$((2))

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    $$\begin{align}{\alpha}_{\text{\rm s},i}(Z)=\frac{20}{\mathrm{In}10}\frac{2\pi }{\lambda}\operatorname{Im}\left({n}_{\text{\rm eff}}^{\text{\rm s},i}\right).\end{align}$$((3))

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    $$\begin{align}\frac{N_2(z)}{N_{\mathrm{Yb}}}&=\bigg\{\displaystyle \frac{\left[{P}_{\mathrm{p}}^{+}(z)+{P}_{\mathrm{p}}^{-}(z)\right]{\sigma}_{\mathrm{ap}}{{\it \Gamma}}_{\mathrm{p}}(z)}{h{\nu}_{\mathrm{p}}{A}_{\mathrm{dope}}(z)}\nonumber\\[4pt]&\quad+\sum \displaystyle\frac{\left[{P}_{\mathrm{s},i}^{+}(z)+{P}_{\mathrm{s},i}^{-}(z)\right]{\sigma}_{\mathrm{as}}{\it \Gamma}_{\mathrm{s},i}(z)}{h{\nu}_{\mathrm s}{A}_{\mathrm{dope}}(z)}\bigg\}\nonumber\\[4pt]&\times\bigg\{\displaystyle\frac{\left[{P}_{\mathrm{p}}^{+}(z)+{P}_{\mathrm{p}}^{-}(z)\right]\left({\sigma}_{\mathrm{ap}}+{\sigma}_{\mathrm{ep}}\right){\it \Gamma}_{\mathrm{p}}(z)} {h{\nu}_{\mathrm p}{A}_{\mathrm{dope}}(z)}\nonumber\\[4pt]&\quad+\sum \displaystyle\frac{\left[{P}_{\mathrm{s},i}^{+}(z)+{P}_{\mathrm{s},i}^{-}(z)\right]\left({\sigma}_{\mathrm{as}}+{\sigma}_{\mathrm{es}}\right){\it \Gamma}_{\mathrm{s},i}(z)}{h{\nu}_{\mathrm s}{A}_{\mathrm{dope}}(z)} +\displaystyle\frac{1}{\tau }\bigg\}^{-1}, \end{align}$$((4))

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    $$\begin{align}\pm \frac{{\mathrm{d}P}_{\mathrm{p}}^{\pm }(z)}{\mathrm{d}z}&={\it \Gamma}_{\mathrm{p}}(z)\left[{\sigma}_{\mathrm{ep}}{N}_2(z)-{\sigma}_{\mathrm{ap}}{N}_1(z)\right]{P}_{\mathrm{p}}^{\pm }(z)\notag\\&\quad{}-\frac{\ln 10}{10}{\alpha}_{\mathrm{p}}(z){P}_{\mathrm{p}}^{\pm }(z),\end{align}$$((5))

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    $$\begin{align}\pm \frac{{\mathrm{d}P}_{\mathrm{s},i}^{\pm }(z)}{\mathrm{d}z}&=\left[{\sigma}_{\mathrm{es}}{N}_2(z)-{\sigma}_{\mathrm{as}}{N}_1(z)\right]{\it \Gamma}_{\mathrm{s},i}(z){P}_{\mathrm{s},i}^{\pm }(z)\notag\\&\quad{}-\frac{\ln 10}{10}{\alpha}_{\mathrm{s},i}(z){P}_{\mathrm{s},i}^{\pm }(z),\end{align}$$((6))

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    $$\begin{align}q=\frac{Q(z)}{A_{\mathrm{dope}}(z)}=\frac{\left(\frac{{\mathrm{d}P}_{\mathrm{p}}^{-}}{\mathrm{d}z}-\frac{{\mathrm{d}P}_{\mathrm{p}}^{+}}{\mathrm{d}z}\right)\times \left(1-\frac{\lambda_{\mathrm{p}}}{\lambda_\mathrm{s}}\right)}{A_{\mathrm{dope}}(z)},\end{align}$$((7))

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    Caijian Xie, Tigang Ning, Jingjing Zheng, Li Pei, Jianshuai Wang, Jing Li, Haidong You, Chuangye Wang, Xuekai Gao. Amplification characteristics in active tapered segmented cladding fiber with large mode area[J]. High Power Laser Science and Engineering, 2021, 9(2): 02000e32
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