Optical hydrogen sensing with metallic photonic crystals and plasmonic metamaterials

In this contribution, we are going to present two plasmonic concepts for hydrogen sensing. Our first concept is based on metallic photonic crystals, where a gold grating together with a thin layer of Pd in combination with a waveguide of WO
₃
can give a strong resonance in the extinction or reflection spectrum. Upon hydrogen exposure, the WO
₃
undergoes a refractive index change, which will shift the spectral resonance. A suitably tuned laser or LED can interrogate this change and give an optical signal. Our second concept is based on a plasmonic metamaterial which comprises a perfect absorber. A layer made from Pd wires as placed on a spacer layer and a gold mirror. Suitable design parameters lead to a zero transmittance as well as zero reflectance for a given wavelength. Upon hydrogen exposure, this perfect absorption is distorted and reflected light can be detected.