Fig. 1. Schematic of proposed metasurface Structure A

Fig. 2. Manufacture procedure chart of required metasurfaces

Fig. 3. Structure A simulation results. (a) Transmission spectrum of Structure A; (b) electric field diagram (E_z) distribution and magnetic field (H_z) current density diagram; (c) toroidal dipole formation diagram, where m denotes magnetic dipole moment and T denotes toroidal magnetic diople moment

Fig. 4. Simulation results of Structure B. (a) Schematic of proposed metasurface Structure B; (b) transmission spectrum of Structure B

Fig. 5. Electric field and magnetic field current density diagrams of Structure B at 1435.9 and 1472.2 nm. (a) Electric field diagram at 1435.9 nm; (b) magnetic field current density diagram at 1435.9 nm; (c) electric field diagram at 1472.2 nm; (d) magnetic field current density diagram at 1472.2 nm

Fig. 6. Multipole and scattering power diagrams. (a) MD formation diagram of single elliptic nanorods in Structure B; (b) TD formation diagram between near elliptic nanorods; (c) scattering power of multipole moments, where EQ and MQ denote electric quadrupole and magnetic quadrupole, respectively

Fig. 7. Simulation results of Structure C. (a) Schematic of proposed metasurface Structure C; (b) transmission spectrum of Structure C

Fig. 8. Electric field and magnetic field diagrams of two sides of D1 and D2 resonant peaks. (a) D1 resonant peak; (b) D2 resonant peak

Fig. 9. Multipole and scattering power diagrams. (a) ED formation diagram of single elliptic nanorod in Structure C, where P denotes electric dipole moment; (b)-(c) TD formation diagram between near elliptic nanorods; (d) scattering powers of multipole moments

Fig. 10. Simulation results of elliptic sensor. (a) Transmission spectra at different volume fractions of methane; (b) resonant wavelengths dip1 and dip2 of two Fano resonances; (c) transmission spectra at different background refractive indexes; (d) resonant wavelength of two Fano resonances when background refractive index varies from 1.00 to 1.06

Fig. 11. Simulation diagram of rectangular gas sensor and gas sensitive film thickness. (a) Rectangular structure diagram; (b) effect of different gas sensitive film thickness on Fano formant

Fig. 12. Simulation results of rectangular sensor. (a) Transmission spectra at different methane volume fractions; (b) resonant wavelength of two Fano resonances when methane volume fraction varies from 0% to 1.5%; (c) transmission spectra at different background refractive indexes; (d) two resonant wavelengths dip1 and dip2 when background refractive index varies from 1.00 to 1.06

Fig. 13. Simulation results under different deflection angles. (a) Transmission diagram of incident light deflection with different angles; (b) transmission intensity of incident light with different deflection angles at formants

Fig. 14. Effect of relative error of rectangle sensor on Fano resonant peak position

Table 1. Formulas for each dipole moment and far-field scattering power in Cartesian coordinate

Table 2. Parameter optimization results

Table 3. Summary of calculation results