Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Testing facility based on waveguide prism coupler for detection, of refraction index variations of thin films exposed to HC gases

Development of a specific facility based on the prism coupler which allows the detection, in guided wave configuration, of refraction index variations of thin films when exposed to HC gases (refractive index variations as low as 10-6 are detected).

An optical set-up based on the prism coupler technique (m-lines) for measuring the sensitivity of thin films to gases (especially butane, propane and ozone) has been developed by CR9 IF. The m-line set-up allows measurement of both static and dynamic optical properties in guided-wave configuration.

By looking at the m-line (dark line) shape obtained in the laser beam reflected on the prism base when a guided wave is coupled in a thin film pressed on the prism base, one is able to deduce static qualitative optical properties of the film: mainly roughness and optical absorption.

Indeed, large and distorted m-line shapes correspond to thin films exhibiting high optical absorption and high diffusion due to roughness. This type of films cannot be used for gas testing because the detection process of the gas is based on the m-line shift during gas exposure.

Thus, thin, non-distorted and well-contrasted m-lines are necessary. By looking, at the m-line angular shift during gas exposure, the refractive index variation, that is the optical sensitivity of the thin-film to the gas, can be measured quite easily and with good reproducibility.

Reported by

Universte Paul Cezanne Aix Marseille III
Case 231
13397 Marseille cedex 20
See on map