Ai Hosoki

A hydrogen curing effect on surface plasmon resonance fiber optic hydrogen sensors using an annealed Au/Ta 2 O 5 /Pd multi-layers film

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.

Multipoint Hydrogen Sensing of Hetero-Core Fiber SPR Tip Sensors With Pseudorandom Noise Code Correlation Reflectometry

In this paper, we describe multipoint hydrogen sensing in real time using surface plasmon resonance (SPR) fiber optic hydrogen tip sensors with Au/Ta2O5/Pd multilayers film combined with a time-domain interrogating system based on pseudorandom noise code correlation reflectometry. This method uses the correlation between a launched pseudorandom noise code signal and its reflection enabling simultaneous measurement at many points along the optical fiber in real time with a high signal-to-noise ratio. In a light intensity-based experiment with an 850-nm LED, the tested three hetero-core optical fiber hydrogen tip sensors proved to be reproducible responses with and without hydrogen absorption, with showing the similar time response and sensitivity compared with those of our previously reported sensor. Multipoint hydrogen detection was demonstrated using four SPR hydrogen tip sensors. Our experimental results showed that four sensors using the 25 nm Au/60 nm Ta2O5/5 nm Pd multilayer film exhibited a response time of ~25 s for a 4% hydrogen concentration. In addition, it was found that all sensors can detect the hydrogen concentration with sufficient sensitivities in real time.

Localized surface plasmon sensor based on gold island films using a hetero-core structured optical fiber

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.

Localized surface plasmon sensor using a hetero-core structured fiber optic with gold island films

This paper reports the effect of applying a gold islands film to the hetero-core structured optical fiber, which is fabricated by annealing thin Au films of 3 nm and 5 nm thicknesses and its sensing performance for the RI changes. We experimentally observe that novel LSPR spectra for 1.333 RIU appear in the visible-to-near-infrared region depending on the shape of Au islands. The absorbance and spectral sensitivities 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.

Hetero-core fiber optic surface plasmon resonance sensor based on Au/Ta 2 O 5 /Pd multi-layer films for hydrogen sensing

Summary form only given. In this paper, we describe a novel fiber optic surface plasmon resonance (SPR) hydrogen sensor based on hetero-core structured fiber optics with multi-layer films of gold (Au), tantalum pentaoxide (Ta2O5) and palladim (Pd) uniformly coated onto a cylindrical cladding surface. The hetero-core fiber sensor has a simple structure with easy fabricationwhich has no need of cladding removal. In addition, the cladding surface could work as a sensing region because the transmitted light is largely leaked into cladding layer owing to the core diameter mismatch between the transmission and inserted fibers. Due to the uniform cylindrical coating SPR resonant curves have been obtained for the cases of 0 and 4% hydrogen with a SPR resonant wavelength shift of 28nm at a concentration of 4% hydrogen in nitrogen for the case of the coating films consisted of 25nm Au/60nm Ta2O5 60/5nm Pd. Sensing properties in terms of response time and sensitivity on hydrogen detection have been experimentally obtained with changing Pd layer thickness in the light intensity-based experiment with an LED operation at 850 nm. It is indicated that a transmitted loss change of approximately 0.23 dB is produced with a response time of 15 sec. for a hydrogen concentration change of 4%, in the case of Au 25 nm, Ta2O5 60nm and Pd 3 nm. The experimental results have revealed that the proposed hydrogen sensor could detect hydrogen concentration with realizing a high sensitivity and as a fast response time as a previously reported sensor.