Abstract
AbstractPractical gas sensors are indispensable for the healthy operation of cutting‐edge hydrogen‐based systems. An optical fiber‐based hydrogen sensor incorporating a robust Fabry–Perot interferometric structure on a fiber tip with high sensitivity, selectivity, and reliability of operation and a micrometer‐scale footprint is demonstrated. The hydrogen‐sensitive volume expansion of palladium provides bi‐metal operation with a silicon nitride mirror to tune the interferometer cavity and therefore the resonance modes by switching the mirror form factor from a flat to convex shape. It does not require any peripherals, including a power supply or data communication modules. In addition to fiber‐inherent advantages, such as remote and multiplexed monitoring without electromagnetic field interference, the sensor guarantees temperature‐ and pressure‐independent operation by adding a simple glass sub‐cavity and microwindows in the mirror layer, respectively. Critically, the sensor highlights reliable operation in a liquid fluid (electrical transformer oil) to monitor hydrogen as its “damage marker” escaping from a mechanical shield or selective gas screen. The detection limit, sensitivity, and response time of the sensor under atmospheric conditions are 15 ppm, 29.6 nm/%, and 12.5 s, respectively. In addition, the unimpaired operation of the sensor in 60 °C transformer oil is verified experimentally.
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