Research And Experiments Of Fiber Optical Hydrogen Sensor

The research of fiber optical hydrogen sensors needs the study of several crossed disciplines, such as thin film for the hydrogen sensing, SPR sensor, analysis of the field distribution around the tapered fibers, the deposition technique, the measurement process and the data analysis.The principle of hydrogen sensing with Pd film is introduced in this thesis as well as several hydrogen sensor models. The alloy Pd90Ag10 is choosed as the sensing film material of the experiments, the creative and advanced SPR hydrogen sensors based on tapered fibers are introduced in the thesis. A novel sensor structure consisting of a combined Pd and gold (Au) thin film is investigated for the optical sensing of hydrogen. Composited Au/Pd hydrogen structure is optimized by a genetic algorithm. It indicates that the optimal layer configuration should be Au(2nm)/Pd(27nm) for achieving the best performance. Compared with the traditional pure palladium thin film hydrogen sensor, the sensitivity of the proposed structure is three times higher. The structure and working principle of the tapered single-mode fiber for hydrogen sensing are designed, fabricated and studied. The techniques for fabricating the tapered fiber sensor are also presented.A new technique for the deposition of high-quality homogeneous Pd90Ag10 thin film on an optical fiber is reported. A special clamp for depositing Pd90Ag10 film on the fiber is designed. The film deposition is processed and the parameters are obtained by the experiment. The experimental set-up for hydrogen sensing includes the light source, gas cell, massive flow controller, stainless steel helical tubing and the detector, etc. The experimental results are also discussed.