Exploration of multi-metallic thin layer/MgF2 in side-polished optical fiber as long-range surface plasmons (LRSPs) alcohol sensor

This paper explores computational and experimental analysis based on configuration using multi-metallic thin layer and dielectric buffer layer (DBL) using side-polished single mode optical fiber as alcohol sensor concentration based on refractive index change. The computational analysis has been carried out using COMSOL Multiphysics 5.3a to investigate the sensing performance of the device. The simulations are based on configuration models with integration of thin layer of silver (Ag), gold (Au) and DBL layer. To observe the effectively function of magnesium fluoride (MgF2) to the reflection dips in the SPR modes, the thickness of MgF2 layer is optimized at 50 nm. The simulation analysis from these configurations namely is MgF2–Au/Ag and MgF2–Au/Ag–MgF2 which performs the best sensing comparison. Configuration of MgF2–Ag–MgF2 shows higher sensitivity value as 2812.5 nm/RIU (Refractive Index Unit) at RI of 1.37–1.38 and 1762.5 nm/RIU at lower RI of 1.33–1.34 for MgF2–Ag configuration. Our calculations also reveal that SPR modes corresponding with MgF2 layer are very sensitive to any changes in the surrounding medium as compared to the conventional SPR sensor reported before. The outcomes indicate the proposed LRSPs based models with specific dielectric of MgF2 found to be an important role in chemical and biological sensing as this structure contributes to high sensitivity, high resolution, and deeper penetration depth where it has great potential for label-free sensing and detection of macromolecules and biomolecules.