In this paper, we investigate the ultimate low loss property for several realistic core shapes in triangular-type air-guiding photonic bandgap fibers (PBGFs) through a full-vector modal solver based on the finite element method. We show that the surface mode free condition is expressed as a normalized silica-ring thickness $T = 0.5$ for any core size and the cladding structural parameters, regardless the core radius of the silica-ring is one of the main factors of dominating the surface mode''s condition, and the wavelength range of the PBG changes on varying the structural parameters of the cladding. Moreover, we propose a novel type of PBGF without surface mode, which exhibits lower scattering losses caused by surface roughness of the silica-ring in comparison to 19 cell-core PBGFs and suppresses the mode coupling between fundamental-like and higher order modes when compared to 37 cell-core PBGFs.
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机译:在本文中,我们通过基于有限元方法的全矢量模态求解器,研究了三角型导气光子带隙光纤(PBGF)中几种实际纤芯形状的极限低损耗特性。我们表明,对于任何纤芯尺寸和包层结构参数,无模态条件均表示为归一化的硅胶环厚度$ T = 0.5 $,而与二氧化硅环的芯半径无关。表面模式的条件,PBG的波长范围会随着包层结构参数的变化而变化。此外,我们提出了一种新型的无表面模式的PBGF,与19种细胞核PBGF相比,它具有较低的由二氧化硅环的表面粗糙度引起的散射损耗,并且与传统的PBGF相比,可抑制基本模式和高阶模式之间的模式耦合。至37个细胞核心PBGF。
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