In this article, a single solid core flat fiber (SSCFF) refractive index sensor based on surface plasmon resonance (SPR) is proposed and analyzed numerically using the finite element method (FEM). The proposed flat fiber consists of a single array of five circular holes. Among them the central hole is made of GeO₂-doped silica which is forming the core. Other holes are filled with air and situated symmetrically on both sides of the central solid core. The upper flat surface of the fiber is coated with a thin plasmonic gold layer which is protected by an active titanium dioxide layers. Analyte is situated on top of these layers. The wavelength interrogation technique is applied to study the coupling characteristics between the core-guided mode and the surface plasmon mode as well as for the refractive index measurement. Numerical analysis results show that this sensor is able to detect high refractive index analytes from 1.49 to 1.54 with a good linear response. Additionally, the dependence of surface plasmonic resonance wavelength on analyte refractive index is studied. The maximum wavelength sensitivity of this sensor is found to be 4782 nm/RIU with a high resolution of 2.09 × 10⁻⁵ RIU. The effects of different structural parameters on loss spectrum are studied in detail to optimize this SSCFF structure. In comparison to traditional PCF, this SSCFF structure is fabrication complexity free as well as a suitable candidate for developing portable devices and high refractive index analyte sensors, particularly chemical and protein sensors.

中文翻译：

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单芯扁平光纤等离子折射率传感器的分析

本文提出了一种基于表面等离振子共振（SPR）的单芯扁平纤维（SSCFF）折射率传感器，并使用有限元方法（FEM）进行了数值分析。提出的扁平光纤由五个圆形孔的单个阵列组成。其中中心孔由GeO ₂制成形成核心的掺杂二氧化硅。其他孔充满空气，并且对称分布在中心实心芯的两侧。纤维的上平面覆盖有一层薄的等离激元金层，该金层由活性二氧化钛层保护。分析物位于这些层的顶部。波长询问技术被用于研究纤芯引导模式和表面等离子体激元模式之间的耦合特性以及用于折射率测量。数值分析结果表明，该传感器能够以良好的线性响应检测1.49至1.54的高折射率分析物。另外，研究了表面等离子体共振波长对分析物折射率的依赖性。^-5 RIU。详细研究了不同结构参数对损耗谱的影响，以优化此SSCFF结构。与传统的PCF相比，这种SSCFF结构没有制造复杂性，并且适合开发便携式设备和高折射率分析物传感器，特别是化学和蛋白质传感器。