Fig. 1. Schematic diagram of gas pressure sensing device

Fig. 2. Optical vernier spectra produced by I₁ and I₂ superposition under different j. (a) j=1; (b) j=2; (c) j=3; (d) j=4

Fig. 3. Vernier spectra and FFT diagrams under different j in experiment. (a)(b) j=1; (c)(d) j=2; (e)(f) j=3; (g)(h) j=4

Fig. 4. Gas pressure test results for sample S1. (a) Drift diagram of internal envelope reference point corresponding to S1 under different air pressures; (b) gas pressure sensitivity corresponding to S1 (inset shows side-view microscopic pictures of sensing and reference Fabry-Pérot interferometers)

Fig. 5. Vernier spectra and their characteristics for different I_A to I_B ratios under constant I_A.(a) I_A∶I_B=2.5∶1.0; (b) I_A∶I_B=3.5∶1.0; (c) I_A∶I_B=4.5∶1.0

Fig. 6. Influence of I_B on envelope feature points under constant I_A. (a) I_A∶I_B=1∶1; (b) I_A∶I_B=3∶1

Fig. 7. Cutting error corresponding to different reference cavity media as function of detuning ratio and sensitivity at L₁=300 μm and j=1. (a) Detuning ratio; (b) sensitivity