Sensitivity Enhancement in D-Shaped Photonic Crystal Fiber Sensors: Gold Versus Silver Plasmonic Layers

Abstract

Surface plasmon resonance (SPR) sensors have attracted great attention in recent years for various applications such as medical diagnosis and bio-chemical materials. Among SPR sensors, D-shaped structures based on photonics crystal fibers (PCFs) have shown very high performance and are easy to use. In this paper, a simple design of SPR sensors based on the D-shaped PCFs with the most optimized geometrical parameters is proposed. Gold and silver are considered as plasmonic layers on the surface of the D-shaped PCF sensor. By performing multiple simulations using the finite-difference eigenmode (FDE) method, various values of gold and silver thicknesses are investigated to achieve the highest sensitivity. The results indicate that the highest sensitivity of 25600 nm/RIU occurs for a gold thickness of 44 nm and an analyte with a refractive index (RI) of 1.41. Meanwhile, for an analyte RI range of 1.29 to 1.40, silver demonstrates greater sensitivity than gold in the same range.