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Hydrogen Sensing Using Thin-Film Perfect Light Absorber

Hydrogen sensing is important in many industrial, biomedical, environmental, and energy applications. Realizing a practical, reliable, and inexpensive hydrogen sensor, however, is an ongoing challenge. Here, we demonstrate hydrogen sensing based on an optically active metal–dielectric–metal (MDM) perfect light absorber. The cavity enables perfect broadband light absorption (>99.999%) with optical losses localized in an ultrathin palladium (Pd) layer. Upon exposure to hydrogen, the Pd layer forms a hydride which actively shifts the cavity minimum reflectance wavelength by ∼60 nm for a hydrogen concentration of 4%. The sensor enjoys extremely high figure of merit. The ease of fabrication, large area, and high sensitivity of our sensor make it an attractive and practical option, especially for miniaturized hydrogen sensors vital for medical and food safety applications.