Ultrasensitive Hydrogen Sensor With Vernier Effect by Dual Parallel Structured Fiber-Optic Fabry-Perot Interferometers

A novel dual parallel structured fiber-optic Fabry-Perot interferometers (FPIs) for ultrasensitive hydrogen (H2)sens-ing using the Vernier effect is proposed and demonstrated. Lever-aging the high mechanical strength and chemical stability of hexag-onal boron nitride (hBN), a nanoscale hydrogen-sensitive thin filmof palladium (Pd)-decorated hBN is prepared and integrated withoptical fiber to form a probe-type FPI hydrogen sensor. To furtherenhance the sensitivity, dual FPIs with similar but different cavitylengths are connected in parallel to exploit the Vernier effect, result-ing in a significant amplification factor. The sensitivity of dual par-allel structured FPIs based on the Vernier effect is-14.19 nm/%,which is 9.27 times higher than that of the individual FPI withinthe H-2 concentration range of 0 similar to 1%. Moreover, as the dualFPIs possess similar temperature coefficients, the Vernier effectreduces the impact of ambient temperature on the sensor, yieldinga temperature coefficient as low as similar to 46 pm/degrees C. Additionally, thesensor offers several advantages, including good repeatability, fastresponse time (similar to 31.3 s), compact structure, easy preparation, andlow cost, making it a practical solution for detecting trace amountsof hydrogen