U-grooved dual-channel plasmonic sensor for simultaneous multi-analyte detection

A photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor is proposed for real-time multianalyte detection. Semicircular U-shaped slots are excavated inside the PCF to facilitate the excitation of surface plasmon polaritons by reducing the distance between the core and external analyte channels. The evanescent field is controlled via engineered scaled-down air holes. A plasmonic metal layer (gold) is deposited over the U-curved microchannel to enhance the surface plasmons. This asymmetric PCF SPR structure enables superior birefringence controllability, which results in a dominant y-polarized response in comparison to the x-polarized mode. The light-guiding and sensor performance parameters are numerically analyzed using the full vector finite element method. The proposed sensor can detect a wide refractive index (RI) range from 1.33 to 1.43. It demonstrates the maximum wavelength sensitivities of 2000 nm/RIU and 12,800 nm/RIU with sensor resolutions of 5 × 10⁻⁵ RIU and 7.813 × 10⁻⁶ RIU for channels 1 and 2, respectively. The sensor also exhibits a maximum amplitude sensitivity of 1119 RIU⁻¹ with a high figure of merit of 474 RIU⁻¹. The simultaneous dual-analyte detection capability and highly sensitive response with a broad detection range make the proposed sensor distinct and will pave the way for miniaturized medical diagnostics and sensing applications.