Hydrogen optical sensors based on magnesium thin films for leak detection in industrial settings

Hydrogen (H₂) infrastructure is the focus of many initiatives for the planned energetic transition, but its volatility and flammability require extensive safety measures to prevent leakages and explosions. Magnesium thin films have been investigated not only for H₂ storage but also as switchable mirrors, which drastically change their optical properties when hydrogenated. Due to their lower cost compared to other hydride-forming or plasmonic metals commonly used in optical sensing, Mg-based H₂ fiber sensors have the potential to be both affordable and effective for scalable deployment in industrial settings. To this end, multilayer thin-film structures with Mg and palladium as adsorption catalyst were deposited on single-mode fiber tips, and H₂ loading/unloading processes were tested in a controlled flow gas setup. In parallel, an optical interrogation system prototype was developed, enabling fast data acquisition of fiber-tip reflectivity across multiple sensing probes at a wavelength of 1550 nm. Preliminary testing suggests fast response times of a few seconds for significant drops in reflectivity, facilitating straightforward detection of H₂ leaks using thresholding methods. Planned future work includes performance comparison with simpler sensing structures, durability and contaminant testing, and response time optimization.