Sensitivity Enhancement of a Plasmonic Sensor Based on a Side Opening Quasi-D-Shaped Optical Fiber with Au Nanowires

The surface plasmon resonance (SPR) of the refractive index (RI) sensor based on a side-opening quasi-D-shaped optical fiber is proposed in this study. This designed sensor uses a gold nanowire (AuNW) to stimulate the plasmon mode. The effect of SPR’s between core guided mode and polaritons of the designed side-opening quasi-D-shaped optical fiber can enhance the sensitivity of the RI, and the polishing of the shorter side can be realized which makes the mechanical strength of the proposed fiber sensor is better than that of other sensors based on the D-shaped fiber. Moreover, the sensor designed in this study is simple to fabricate, as the side opening of the quasi-D-shaped optical fiber can be readily filled with a sensing medium, and it offers the advantages of reusability. The key parameters of the proposed sensor have been evaluated using the finite element method-based COMSOL Multiphysics. Various structural design parameters, including the width of the U-shaped groove, the diameter of the AuNW, and the distance of the opening depth from the core, are optimized. Results indicate enhanced sensitivity at 14.5 μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}m/RIU. The resolution is 6.896×10-6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$6.896 \times 10^{-6}$$\end{document} RIU in the sensing RI range of 1.33–1.41. The maximum amplitude sensitivity is 453 RIU -1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-1}$$\end{document} at the sensing RI of 1.40. The novel SPR sensor is an excellent candidate for application in biochemical sensors.