A surface plasmon resonance (SPR) sensor based on a photonic crystal fiber (PCF) is proposed for low refractive index (RI) detection. The core of PCF is formed by two-layer air walls and either layer is composed of six identical sector rings with negative curvature. Plasmonic material gold (Au) is coated on the external cladding surface. Finite element method (FEM) is applied to investigate the performance of the SPR sensor. Results show that the sensor is independent of polarization due to the coincident coupling properties of the two polarized modes. Additionally, in low RI ranging from 1.20 to 1.33, the sensor keeps a high spectral sensitivity with an average value of 7738 nm/RIU. When RI varies from 1.32 to 1.33, the resolution reaches to its maximum of 8.3 × 10⁻⁶. The proposed sensor shows much significance in low RI detection, which is promising in real-time measurement for medical, water pollution, and humidity.

中文翻译：

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基于光子晶体光纤的偏振无关SPR传感器，用于低RI检测

提出了一种基于光子晶体光纤（PCF）的表面等离子体共振（SPR）传感器，用于低折射率（RI）检测。PCF的核心由两层气隙形成，每一层都由六个相同的扇形环组成，并具有负曲率。等离子材料金（Au）涂覆在外部包层表面。有限元方法（FEM）用于研究SPR传感器的性能。结果表明，由于两种偏振模式的重合特性，传感器与偏振无关。此外，在低RI范围为1.20至1.33的情况下，该传感器可保持较高的光谱灵敏度，平均值为7738 nm / RIU。当RI在1.32至1.33之间变化时，分辨率达到最大值8.3×10 ^-6。所提出的传感器在低RI检测中显示出重要意义，这对于医疗，水污染和湿度的实时测量很有希望。