Optical hydrogen detection with periodic subwavelength palladiumhole arrays

The extraordinary transmission of infrared light through subwavelength rectangular hole arrays of palladium is used to detect hydrogen. The main resonance peak of rectangular hole arrays is found to shift upon exposure to hydrogen. Experimental evidence of the change in the Pd phase, producing a shift toward longer wavelengths of the main resonance peak, is presented and supported by simulations that agree with experimental observation. The all-optical and selective detection scheme of hydrogen produces large peak shifts that enable the detection of hydrogen concentration near the lower flammability threshold in air.