Gold island fiber optic sensor for refractive index sensing

A fiber optic chemical sensor based on gold island surface plasmon excitati on is presented. The sensing part of the fiber is the end of the fiber onto which a thin layer of gold has been deposited to form a particulate surfac e. Annealing the gold reshapes the particles and produces an optical absorb ance near 535 nm with the fiber in air. The optical absorption resonance of the gold particles is shifted if the fiber is immersed in a medium other t han air. These resonance shifts are examined by transmission spectroscopy t hrough the fiber. Experimental results for the sensitivity and dynamic rang e in the measurement of liquid solutions are in agreement with a basic theo retical model that characterizes the surface plasmon using nonretarded elec trodynamics. (C) 2000 Elsevier Science S.A. All rights reserved.