Fabrication of hydrogen gas sensor using sputtered palladium-copper composite on tapered optical fiber

Abstract In this study, we fabricated a hydrogen (H 2 ) gas sensor based on tapered optical fiber using sputtering method. Also, as the first attempt, we explored how palladium (Pd) and palladium-copper (Pd-Cu) coatings, deposited using the sputtering method (RF and DC), affect tapered optical fibers as H 2 gas sensors (ranging from 1 to 8% H 2 ). It investigates changes in sensor output power, response and recovery times, and the influence of fiber tapering angle on output power. The investigation reveals that two main factors, including permeability and elasto-optic effect significantly impact the results. At H 2 concentrations of 1 to 3%, permeability predominantly affects Pd sensors, yielding better output power changes and sensitivity than Pd-Cu tapered optical fiber sensors. Conversely, at higher H 2 concentrations (4 to 8%), the dominant factors appear to be permeability as well as elasto-optic effect. These characteristics have a greater influence in the Pd-Cu layer at higher H 2 concentration, resulting in smoother slope in response to H 2 . Due to higher permeability, Pd sensors reach saturation faster, while Pd-Cu sensors exhibit more linear changes with increasing H 2 levels and do not saturate like Pd sensors very fast. Moreover, the study shows that a larger tapering angle can enhance the output power of Pd-Cu tapered optical fiber sensors.