Physical mechanism of reflectance inversion in hydrogen gas sensor with Pd/PVDF structures

The physical mechanism of the reflectance inversion phenomena observed in t hin-film Pd on polyvinylidene fluoride (PVDF) optical hydrogen sensor struc tures (Pd/PVDF) upon exposure to hydrogen gas has been investigated. Based on experimental observations using sensors with or without a metallic back- surface coating, a theoretical model taking into account the infinite optic al interreflections within the transparent polymer PVDF has been proposed. The understandings of the origin of the reflectance inversion is helpful in optimizing the design and performance of optical hydrogen sensors with Pd- layer active element structures. (C) 2001 Published by Elsevier Science B.V .