Dual-parameter measurements of refractive index and methane concentration based on electromagnetic Fano resonance are proposed. Two independent Fano resonances can be produced through electric dipole and toroidal dipole resonance in an all-dielectric metasurface separately. The linear relationship between the spectral peak-shifts and the parameters to be measured will be obtained directly. The refractive index (RI) sensitivity and gas sensitivity are 1305.6 nm/refractive index unit (RIU), −0.295 nm/% for one resonance peak (dip1), and 456.6 nm/RIU, −0.61 nm/% for another resonance peak (dip2). Such a metasurface has simpler structure and higher sensitivity, which is beneficial for environmental gas monitoring or multi-parameter measurements.

A high-sensitive multi-parameter gas sensor composed of symmetric dual side-coupled ring resonators in a metallic-dielectric-metallic (MDM) structure is investigated by the finite difference time domain (FDTD) method. The dual side-coupled resonators have lower transmission dip and faster response due to the superposition of the outgoing fields’ amplitude of the symmetric dual resonators, which is very beneficial for detection. Two independently tunable transmission dips are achieved by expanding the ring resonator in ${x}$ -direction, making it possible for dual-parameter sensing. The electric and magnetic distribution characteristics at the two resonant wavelengths are analyzed. Another plasmonic structure expanded along both sides in a central resonator-straight waveguide way is also investigated, and the former structure expanded in ${x}$ -direction works better in detection difficulty and structural utilization. After optimizing the radius and position of ring resonators, the refractive index sensitivities of cavity A and B can reach 2427 nm/RIU and 2431.9 nm/RIU, respectively. The methane and hydrogen sensitivities are −9.213 nm/% and −1.65 nm/% with an extremely high linearity, after coating the methane and hydrogen gas-sensitive film in cavity A and B respectively. This investigation provides an effective way for the design of multi-parameter high-sensitive independently tunable sensors.