Spatially tuned photonic crystal fiber sensor mimics visible and near-infrared regimes for wide-range multi-analyte detection

In this study, we report a novel dual-core photonic crystal fiber (PCF) sensor designed to mimic visible (VIS) and near-infrared (n-IR) regimes through the utilization of surface plasmon resonance (SPR). The sensor design aims to achieve wide refractive index (IR) sensing capabilities and simultaneous detection of multiple analytes. The PCF design features two concentric rings forming the cladding in a circular lattice configuration, strategically omitting air holes on both sides adjacent to the metal layer to enhance coupling effects. To induce plasmon resonance, a chemically inert thin layer of gold (Au) is applied to the half-ellipse-shaped sensing channel. Utilizing the finite element method in COMSOL Multiphysics, we systematically explore the optical characteristics of the proposed SPR-based PCF. Operating within the VIS band, the sensor demonstrates the ability to simultaneously detect multiple analytes within the range of 1.35–1.44. Furthermore, it exhibits a wider RI sensing range from 1.15 to 1.44 in the n-IR band. The sensor showcases a wavelength sensitivity of ∼ 1840 nm/RIU and an amplitude sensitivity of ∼ 168.13 RIU−1 with a resolution of 6.71 × 10−5 RIU in the n-IR band. Conversely, in the VIS band, the sensor demonstrates higher sensitivity, reaching up to 4520 nm/RIU, and an amplitude sensitivity of ∼ 1093.29 RIU−1 with a resolution of 5.43 × 10–5 RIU. These findings underscore the potential of the dual-core SPR-based PCF sensor for versatile and high-performance applications in RI sensing and multi-analyte detection for VIS and n-IR spectroscopy.