Highly Sensitive Dual-Core PCF Based Plasmonic Refractive Index Sensor for Low Refractive Index Detection

A highly sensitive surface plasmon resonance (SPR) sensor on a dual-core photonic crystal fiber (PCF) for low refractive index (RI) detection is presented in this paper. Plasmonic material silver (Ag) is deposited outside of the fiber structure to detect changes of the surrounding medium's refractive index. To prevent oxidation a thin layer of titanium dioxide (TiO₂) is employed on top of the silver. The sensor shows maximum wavelength sensitivity and amplitude sensitivity of 116,000 nm/RIU and 2452 RIU^−1 with corresponding resolutions (R) of 8.62 × 10^−7 and 5.55 × 10^−6 RIU, respectively. A thorough study of the relevant literature yielded that these attained sensitivities in both interrogation methods are the highest among reported PCF-SPR sensors to date. In addition, the sensor possesses a very high figure of merit of 2320 in the sensing range of 1.29 to 1.39. Therefore, it would be a suitable candidate for pharmaceutical inspection, organic chemical sensing, and biosensing and other analytes detection.