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In this paper, a response time of the surface plasmon resonance fiber optic hydrogen sensor has successfully improved with keeping sensor sensitivity high by means of hydrogen curing (immersing) process of annealed Au/Ta2O5/ Pd multi-layers film. The hydrogen curing effect on the response time and sensitivity has been experimentally revealed by changing the annealing temperatures of 400, 600, 800°C and through observing the optical loss change in the H2 curing process. When the 25-nm Au/60-nm Ta2O5/10-nm Pd multi-layers film annealed at 600°C is cured with 4% H2/N2 mixture, it is found that a lot of nano-sized cracks were produced on the Pd surface. After H2 curing process, the response time is improved to be 8 s, which is two times faster than previous reported one in the case of the 25-nm Au/60-nm Ta2O5/3-nm Pd multi-layers film with keeping the sensor sensitivity of 0.27 dB for 4% hydrogen adding. Discussions most likely responsible for this effect are given by introducing the α-β transition Pd structure in the H2 curing process.

This paper reports the effect of applying an Au island film to the hetero-core structured optical fiber, which is fabricated by annealing thin Au films with thicknesses of 3 and 5 nm and its sensing performance for the refractive index changes. We experimentally observe that novel localized surface plasmon resonance spectra for 1.333 RIU appear in the visible-to-near-infrared region, depending on the shape of Au islands. The absorbance and spectral sensitivity for a given refractive index region of the tested solvents were obtained to be 4.81 AU/RIU and 517 nm/RIU, respectively, in the range of 1.333-1.384 RIU in the case of 5 nm thick Au film annealed at 900°C.

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