A surface plasmon resonance hydrogen sensor using Au/Ta₂O ₅/Pd multi-layers on hetero-core optical fiber structures

A novel fiber optic surface plasmon resonance (SPR) hydrogen sensor has been developed based on hetero-core structured fiber optics with multi-layer films of gold (Au), tantalum pentaoxide (Ta₂O₅) and palladium (Pd) uniformly coated onto a cylindrical cladding surface. We experimentally observed that the SPR resonant wavelength is shifted 28 nm with 4%-hydrogen concentration in nitrogen. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.23 dB was induced with a response time of 15 s for 4% hydrogen in the case of 25-nm Au, 60-nm Ta₂O₅ and 3-nm Pd multi-layer film. The proposed sensor has successfully detected hydrogen concentrations with a high sensitivity despite the usage of very thin Pd films.