Fig. 1. Schematic diagrams of the optical fiber hydrogen sensor based on a Pd-coated microcantilever. (a) 3D image; (b) 2D image

Fig. 2. Measurement of Pd film thickness using a white light interferometer after different sputtering time. (a) Sputtering for 3 min (14 nm); (b) sputtering for 6 min (24 nm)

Fig. 3. Scanning electron microscopy images of integrated microcantilever on the fiber end face viewed from different angles. (a) 45° view; (b) top view; (c) side view (cylinder is an SMF and the triangular structure is the microcantilever)

Fig. 4. Experimental results. (a)‒(f) Relationship between the reflection spectrum of the sensor and the volume fraction of hydrogen when the Pd film thickness is 24 nm; (g) comparison of the sensitivities of microcantilever sensors with different Pd film thicknesses (T₁∶24 nm Pd film thickness. T₂∶‍14 nm Pd film thickness. The lines through the points represent fittings with an exponential function); (h) variation relationship of corresponding chamber length when hydrogen volume fraction changes from 0 to 0.2%

Fig. 5. Experimental results. (a) Sensor repeatability testing under different hydrogen volume fractions; (b) sensor response time at hydrogen volume fraction of 4.0%