A Broadband D-Shaped Photonic Crystal Fiber Sensor via Surface Plasmon Resonance for Different Analytes with a Large Range of Refractive Index Detection

A D-shaped photonic crystal fiber (PCF) refractive index (RI) sensor based on surface plasmon resonance (SPR) is proposed. We used an open-ring channel coated with a gold film to excite the plasmonic modes. The coupling properties and sensing performance of this structure are analyzed using the finite element method. Different from the related D-shaped PCF refractive sensor, the sensing performance of different positions of analyte placement is investigated. Through simulation analysis by different positions of analyte placement, it is revealed different RI detection. When the analyte is distributed across the entire outer ring region, the sensor exhibits the RI detection range from 1.2 to 1.34. The sensor achieves a maximum spectral sensitivity of 2000 nm/RIU and a resolution of 2 × 10⁻³ RIU. When the analyte is confined exclusively to the upper aperture, the sensor’s RI detection range extends from 1.33 to 1.46. The simulated results show that the proposed sensor achieves a maximum spectral sensitivity of 5600 nm/RIU and a resolution of 8 × 10⁻⁴ RIU. Regardless of which of the two positions the analyte is placed, the proposed D-shaped photonic crystal fiber (D-PCF) sensor has a broad operating wavelength. The excellent sensing performance makes the proposed SPR sensor a competitive candidate in RI detection applications.