Monitoring the diffusion of vapour molecules in polymer films using SP-leaky-mode spectroscopy

Vapour molecules that diffuse into a polymer film cause refractive index ch anges that lead to a signal in an optical sensor device. In a gas-sensor ba sed on surface-plasmon-leaky-mode spectroscopy refractive index changes ind uce measurable resonance shifts in the reflectivity spectrum depending on t he present vapour concentration. The measurement of the whole angular spect rum of a glass/metal/polymer multilayer system provides detailed informatio n about the optical properties of the layers. Recording the resonance shift s with time leads to the dynamic behaviour of the diffusion process, i.e. t he diffusion coefficient of the vapour molecule in the particular polymer c an be determined. (C) 1998 Elsevier Science S.A. All rights reserved.