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 changes that lead to a signal in an optical sensor device. In a gas-sensor based on surface-plasmon-leaky-mode spectroscopy refractive index changes induce measurable resonance shifts in the reflectivity spectrum depending on the present vapour concentration. The measurement of the whole angular spectrum of a glass/metal/polymer multilayer system provides detailed information about the optical properties of the layers. Recording the resonance shifts with time leads to the dynamic behaviour of the diffusion process, i.e. the diffusion coefficient of the vapour molecule in the particular polymer can be determined. (C) 1998 Elsevier Science S.A. All rights reserved.