PCF-based multi-analyte refractive index sensor for pathogen detection in water

A photonic crystal fiber (PCF)-based multi-analyte refractive index sensor is introduced in this study for the detection of four waterborne pathogens: Vibrio cholerae, Bacillus anthracis, Escherichia coli, and Enterococcus faecalis. The sensor comprises a tri-core structure with hexagonal rings encased in a silica substrate. Two selective holes are infused with water samples, enabling concurrent detection of two analytes. The sensor integrates liquid-silica mode coupling as its sensing mechanism. The couplings are precisely estimated and numerically evaluated using a finite-element method (FEM)-based simulation tool. The optimization of the sensor's structural characteristics resulted in wavelength sensitivity of 6386 nm/RIU, 7104 nm/RIU, 8510 nm/RIU, and 3409 nm/RIU for sample pairs of V. cholerae-pure water, V. cholerae-V. cholerae, V. cholerae-B. anthracis, and E. coli-V. cholerae, respectively. Furthermore, the sensor exhibits the highest wavelength resolution of 1.59x10-5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {1.59} \times \text {10}<^>{-5}$$\end{document} RIU and figure of merit of 142 RIU-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {RIU}<^>{-1}$$\end{document} and is also assessed for detection limit, detection accuracy, and signal-to-noise ratio. Featuring a straightforward design and remarkable sensing capabilities, the proposed sensor is anticipated to be exceptionally effective at detecting waterborne pathogens, with potential to excel in identifying chemicals, biomedical substances, and other diverse analytes.