Application of a liquid sensor based on surface plasma wave excitation to distinguish methyl alcohol from ethyl alcohol

A liquid sensor based on surface plasma wave (SPW) excitation was fabricated by the deposition of an optimized thickness of gold metal film on a prism. This sensor was applied to measure the reflectivity versus resonant angle of the SPW excitation using water, methyl alcohol, and ethyl alcohol of various concentrations as dielectric. An attempt was also made to theoretically estimate the position of the dip, and the result is in good agreement with experiment. The measured positions of dips, which correspond to the resonant angle of the SPW mode, varied with the species of dielectric, making it easy to distinguish methyl alcohol from ethyl alcohol. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)03701-6].