Dual-side polished SPR-PCF ultra-wide refractive index sensor with high amplitude sensitivity

A highly sensitive polished photonic crystal fiber (PCF) sensor with an external sensing method has been proposed, which utilizes the surface plasmon resonance (SPR) optical sensing technique. The aim of this study is to develop a sensor which can be utilized to detect a vast range of analyte samples, ranging from low refractive index (RI) chemicals to high RI biomedical applications, while also considering the cost and ease of fabrication. The two polished sides are coated with a plasmonic material called aluminum-doped zinc oxide (AZO) that enhances the coupling strength and enables the SPR technology. The finite element method is employed to analyze the PCF numerically, which confirms a RI spanning from 1.18 to 1.45 for analyte detection, the highest detection extent found for AZO. After analysis, the maximum value of amplitude sensitivity was found to be 6312.34 RIU-1, and the highest wavelength sensitivity of 20 500 nm RIU-1 was attained. Moreover, the PCF provides a maximum amplitude resolution of 1.58 x 10-6 RIU and wavelength resolution of 4.88 x 10-6 RIU. The confinement loss was also fairly low, perfect for longer sensor lengths. The figure of merit resulted to be 820.924 RIU-1. This SPR-PCF sensor offers high stability during operation due to its high linearity in the visible and infrared spectrum. The proposed sensor has the merits of an extremely wide range of RI detection with high sensitivity and a significantly improved polished design, which can be used in various applications, including chemical analysis, gas detection, and biological cell detection with extremely high accuracy.