Construction and evaluation of a gold-deposited optical fiber sensor system for measurements of refractive indices of alcohols

摘要

A gold-deposited optical fiber sensor system using surface plasmon resonance (SPR) in a gold film (45 nm) around an unclad core was constructed and the system was evaluated for quantitative analyses of various alcohols. A small change of 0.0001 refractive index (RI) units in the refractivity can be measured. The response time of the sensor system is less than 0.5 min. The straight line with a correlation coefficient of 0.997 in the calibration curve for methanol solutions of benzyl alcohol was obtained below 6% (v/v). The response curve of the sensor to the wide range of refractive indices from 1.33 to 1.54 has a broad and sharp minimum at 1.374 and 1.462 RI units, respectively. The former minimum due to the SPR phenomenon shifts to a lower refractivity as the film becomes thicker. The refractivity of the latter minimum is very close to that of the core of the optical fiber. Surface morphologies of deposited gold films on glass and a variation in resistance of the films with various thicknesses show that the minimum is due to the leakage of light through defects in the thin deposited gold film to the sample solution with the same refractivity as that of the core. (C) 2003 Elsevier B.V. All rights reserved. [References: 44]