Detection of hydrogen by means of a thin film interferometer Fabry-Perot applying a-WO3 layers

The paper presents a layered sensing structure that permits to detect and to measure the concentration of hydrogen in a gaseous medium. This metal-dielectric-metal structure is a layered Fabry-Perot interferometer. The resonant cavity is made of WO3. The choice of just this material was dictated by its chemochromatic properties, i.e. the change of the optical properties due to the absorption of atomic hydrogen. In result of the absorption of H+ and e- the purely dielectric layer becomes a lost layer, displaying attenuation. The catalysis of molecular hydrogen to atomic hydrogen occurs in the palladium layer, which is also one of the mirrors of the interferometer. The measurement of the hydrogen concentration consists in the scanning of the angular variation of the interference peak position due to the absorption of hydrogen. The change of the peak position results from the change of the optical parameters of the Pd and WO3 layers.