Sub-wavelength palladium antenna arrays for hydrogen optical detection in the infrared region

Sub-wavelength scaled metallic structures have been studied as sensing elements in new optical devices because these structures enable strong enhancement of the electric field. Among these structures, nano-antenna arrays play a special role for antennas are known to realize both functions of source and detection for radiation. In this paper, rectangular shaped palladium (Pd) sub-wavelength nano-antenna arrays were applied to the detection of permittivity change of the antennas made of Pd that forms Pd hydride when exposed to hydrogen (H-2). The dip of the extinction spectrum was shifted toward longer wavelengths. The shape, periodicity, and Permittivity dependence of the extinction spectrum of the nano-antenna arrays were investigated through computational and experimental studies. The peak position and sharpness of the extinction spectrum were tailored by varying the period of the arrayed structure. Extinction dip was shifted by 164 nm when exposed to 2% H-2. (C) 2014 The Japan Society of Applied Physics