Design and optimization of the optical fiber surface plasmon resonance hydrogen sensor based on wavelength modulation

An optimal design of an optical fiber surface plasmon resonance (SPR) sensor based on wavelength modulation for hydrogen (H2) concentration detection is presented in this paper. The proposed sensor consists of a multimode fiber with a sensing region. The transfer matrix method for multilayer model is applied to calculate the normalized output power. Simulation results show that an optical fiber SPR hydrogen sensor based on wavelength modulation using platinum/tungsten oxide (Pt/WO3) composite films as sensitive materials has high sensitivity and good resolution, and the modulation layer with appropriate thickness and suitable material type plays an assistant role in strengthening SPR. The thickness of each layer is optimized. For the optimized structure (the 35 nm silver (Ag)/100 nm silica (SiO2)/180 nm WO3/3 nm Pt multilayer), the resonant wavelength theoretically shifts 17.4 nm at a concentration of 2% hydrogen in argon (Ar). Compared with other hydrogen sensors, the designed sensor can exhibit better performance.