Plasmonic D-Shaped Bimetallic Coating Refractive Index Sensor

In this work, we present a simple yet highly effective surface plasmon resonance (SPR) biosensor for refractive index (RI) detection in the range of near-infrared (IR). The PCF is coated with an Au layer that is strongly attached to the silica surface of the fiber using titanium dioxide in the shape of a thin adhesive layer. The proposed sensor boasts impressive performance characteristics, including maximum wavelength interrogation sensitivity (WS) of 17,500 nm/RIU in the detection range of 1.37–1.41 and an average sensitivity of 12,500 nm/RIU. Moreover, it demonstrates a max amplitude sensitivity (AS) of 8725.56 RIU −1 and provides a theoretical maximal resolution of 8 × 10 −6 RIU using both amplitude and wavelength interrogation techniques. These results represent the highest sensitivity and resolution ever recorded for a PCF-SPR sensor, making it an ideal candidate for detecting biomolecules, chemical analytes, organic compounds, and other substances. The positive outcomes obtained across all analytes tested demonstrate the reliability and robustness of our sensor.