Design of all dielectric metasurface methane sensor based on Fano resonance

Compared with traditional methane sensors, metasurface methane sensors have advantages such as high sensitivity, stable performance, miniaturization, integration, and multi functional customizability. It better meets the application needs in complex environments such as coal mines. This paper proposes an all dielectric type metasurface methane sensor based on Fano resonance. The metasurface structure consists of periodic silicon nanostructures and SiO₂ substrates, consisting of four square silicon ring nanostructures and a central silicon nanoblock. By changing the geometric parameters, the effect on the Fano resonance of the all dielectric metasurface structure is observed. The results show the following points. Considering the quality factor and modulation depth of the structure, the center distance of the square silicon ring should be 1000 nm, the inner edge length of the square silicon ring should be 100 nm, and the edge length of the silicon nanoblock should be 200 nm. At this time, the quality factor is 227.60, and the modulation depth is 99.98%, which is close to 100%. By coating methane gas sensing thin films within the metasurface structure to achieve sensing and detection functions, combined with the extremely narrow linewidth Fano resonance features and significant local field enhancement effect, high-precision detection of methane gas is achieved. The simulation results show that the sensitivity of the all dielectric metasurface sensor to methane volume fraction is −0.953 nm/%. The change in methane volume fraction is linearly related to the shift of the resonance peak, indicating good monitoring performance. The refractive index sensitivity of the all dielectric metasurface sensor is as high as 883.95 nm/RIU. The resonance peak offset is linearly related to the environmental refractive index increment, which can be used to detect changes in environmental refractive index.