Complex grating-based plasmonic hydrogen sensors.
(A) Schematic of a metallic photonic crystal slab which incorporates WO3 as the waveguide layer material. (B) Wavelength shift of the extinction dip in TM polarization for various H2 concentrations (A–B adapted with permission from . Copyright 2010 Optical Society of America). (C) SEM image of a subwavelength Pd hole array. (D) Transmittance change for a hole array with an aspect ratio of 1.6 when exposed to 2 vol.% H2 in dry air (C–D reprinted with permission from . Copyright 2009, AIP Publishing LLC). (E) Schematic of the palladium-based perfect absorber hydrogen sensor. (F) Reflectance spectra of an optimized perfect absorber structure in N2 and when exposed to 1 and 4 vol.% H2 in N2 (E–F reprinted with permission from . Copyright 2011 American Chemical Society).