Energy consumption has increased exponentially due to population growth leading to an increasing impact on natural resources. Green hydrogen (H2) offers a safer alternative to fossil fuels, making it a promising alternative for sustainable energy consumption. However, due to H2's flammability it is crucial to monitor its concentrations in the environment. Optical sensors have been developed to monitor H2 concentrations in harsh environments with high sensitivity and remote measurement. In this work, a numerical study and experimental validation of an optical fiber sensor based on Surface Plasmon Resonance (SPR) for H2 detection are presented. This sensor is composed of a multi-mode fiber with a SPR structure of a metal/dielectric/Pd, where the Pd acts as a sensitive layer. The plasmonic active materials studied are Ag and Au, while TiO2 and SiO2 are used as dielectrics, finding that the metal materials have more impact on the SPR band definition, while the dielectric layers have an impact on the band spectral position. The optimized configuration with 25nm/60nm/3nm of Au/TiO2/Pd was experimentally developed, obtaining a wavelength shift of 19nm for 2kPa of H2, validating the numerical results, and confirming the possibility of using this type of system for H2 detection.
The increasing demand for precise chemical and biological sensing has led to the development of highly efficient plasmonic optical fiber sensors. Therefore, it is essential to optimize and match the operating wavelength region of both the optical fiber configuration and localized surface plasmon resonance of nanoparticles (NPs). This can be achieved by developing NPs that can reach resonance at near-infrared wavelengths, where refractive index sensitivity is enhanced, and silica optical fibers have lower losses. High aspect-ratio bimetallic Au@Ag nanorods and different side-polished fiber structures are tested using numerical simulations. The selected optical fiber configuration was based on a side- polished fiber with a 1 mm polished section. It is compared power losses and power at the NP interface for two configurations: a step-index single-mode fiber (SMF) with core/cladding diameters of 8.2/125 µm and a multimode graded-index fiber (GIF) with 62.5/125 µm at various polishing depths. The results showed that the best performance for both configurations was achieved at similar polishing depths, namely 59.5 and 55.2 µm for the SMF and GIF, respectively. The optical impact of retardation effects due to the proximity with the fiber structure were also observed, which caused a reduction in sensitivity from 1750 nm/RIU to 1500 nm/RIU and a red-shift of
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