Multiple gold island layers on a fiber core: a promising sensing device

Optical fibers are being used more and more as chemical sensors or biosenso rs. Some of these devices are based on thin film plasmon excitation in whic h a metal coating is evaporated onto the core or end of an etched optical f iber. A new sensor configuration is presented for detecting liquid adsorbat es with different indices of refraction. Instead of exciting surface plasmo n waves on a thin film, localized surface plasma waves are excited on metal islands. The fiber is coated with three very thin layers of gold. Each lay er is annealed before the next layer is evaporated onto it. This is done to avoid any light leakage, a problem discovered in a prior version with only one gold coating. Different sets of fibers were tested and sensitive and r eproducible results for liquids with refraction indices varying from 1.563 to 1.683 were obtained. (C) 2001 Society of Photo-Optical Instrumentation E ngineers.