Diamond-like carbon on gold and titanium dioxide grating-enhanced D-shaped PCF SPR refractive index sensor

Abstract

In this work, a novel D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) refractive index sensor structure is designed, optimized, and numerically investigated via the finite element method (FEM)-based COMSOL Multiphysics in the near-infrared region incorporating diamond-like carbon (DLC), gold (Au), and titanium dioxide (TiO₂) grating. According to the available literature, the integration of DLC thin film with a D-shaped PCF SPR sensor has not been explored. The optical and chemical properties of DLC thin film are obtained through our experimental study by utilizing the Plasma Enhanced Chemical Vapor Deposition method. The refractive index dispersion of DLC film is used in FEM based numerical analysis. Due to DLC's key advantages, including high hardness and strong wear resistance, corrosion resistance, chemical stability, biocompatibility and hydrophobicity, it is an ideal material for sensor applications. Regarding these advantages, we were motivated to demonstrate the applicability of DLC on the D-shaped PCF-SPR sensor structure for the first time in the literature. From the FEM study, it is observed that compared to Au/TiO₂ and Au/TiO₂/DLC, the sensor with DLC showed a 43.61 % improvement, and sensitivity was calculated as 31745 nm/RIU in the 1.39–1.40 refractive index range. Numerical results indicate that integrating DLC into the D-shaped PCF-SPR sensor structure is an effective approach. Compared to other related works, the designed PCF SPR sensor has improved responses, a longer lifespan, and a wider sensing area in addition to DLC advantages. Because of these advantages, the novel proposed D-shaped PCF SPR structure with DLC demonstrates remarkable sensing potential for use in applications including chemical, medical, biochemical, and other sensing applications.