Design of intrinsically self-referenced plasmonic grating sensor for hydrogen detection via dual-mode resonance

Hydrogen is a clean energy needs reliable sensing technologies due to its flammable and invisible properties. Surface plasmon resonance sensors based on palladium (Pd) are highly attractive to hydrogen sensing. However, conventional Pd sensors for hydrogen sensing are single-resonance detection. This mechanism makes sensor highly susceptible to external disturbances. A dual-mode resonance hydrogen sensor with an intrinsically self-referenced detection mechanism is proposed in this work. The electric field distributions and theoretical analysis of structure parameters are discussed with finite-difference time-domain methods. The sensor supports two resonance modes. By simultaneously detecting sensing and reference channels to overcome the influence of ambient refractive index change. The optimized sensor achieves a resonance wavelength shift of 16 nm and a relative reflectance change of 120% under 4% H₂ exposure. The dielectric grating is fabricated to show its robustness against fabrication tolerances. This proposed dual-mode structure shows significant potential for hydrogen sensing applications.