Photonic Crystal Fiber Sensor Based on Surface Plasmon Resonance Sensor with Ultra-High Sensitivity

An ultra-sensitive photonic crystal optical fiber sensor based on surface plasmon resonance (SPR) is designed and analyzed. The D-shaped optical fiber is symmetrically coated with two layers of gold along the Y-axis, and the pores inside the fiber follow the PCF stacking structure. The D-symmetric double gold layer structure is based on the surface dissociative excitation resonance excitation mechanism, and the Y-symmetric double gold layer design enhances the electromagnetic coupling at the metal-medium interface, providing more stable excitation conditions for the SPR effect. This structure can effectively modulate the propagation characteristics of the surface plasma wave, thereby improving the response of the sensor to changes in refractive index. The sensing characteristics are investigated using the finite element method. It shows ultra-high sensitivity and low loss, as exemplified by a maximum wavelength sensitivity of 70,000 nm/RIU, an average wavelength sensitivity of 5150 nm/RIU in the RI range between 1.23 and 1.43. In addition, the sensor has a resolution of 1.43 × 10⁻⁷ RIU, a factor of merit (FOM) of 834.4 RIU⁻¹, and a maximum loss of only 2.59 dB/cm, greatly improving optical transmission efficiency. The outstanding results suggest immense in various applications, including biosensing, virus detection, and organic chemistry. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025