Quantum nanoplasmonic alchemy: transforming yttrium into an on-chip hydrogen sensor

We present a nanoplasmonic hydrogen sensor based on a gold–yttrium–platinum plasmonic waveguide, numerically investigated using rigorous coupled wave analysis (RCWA). Upon hydrogen absorption, the yttrium layer undergoes a reversible phase transition from metallic to semiconducting, which alters its dielectric permittivity and modulates the optical response of the device. These hydrogen-induced changes lead to a pronounced plasmon resonance red-shift (Δλ) and enhanced differential reflectance (ΔR), providing a sensitive optical readout of hydrogen concentration (H/Y). By tuning the waveguide height, air gap, and yttrium hydride thickness, the sensor response is further optimized, demonstrating broad spectral tunability and improved detection sensitivity compared to conventional palladium-based approaches. This work highlights yttrium hydride as a novel and tunable plasmonic material, establishing its potential for practical, real-time hydrogen detection in energy storage systems, industrial safety monitoring, and environmental applications.