Fig. 1. The meta-surface structure of the terahertz SSP based on grating coupling. (a) Schematic diagram of the grating-coupled SSP meta-surface structure; (b) schematic diagram of unit cell structure of the meta-surface

Fig. 2. The meta-surface structure and transmission properties. (a) Schematic diagram of the equivalent grating coupler; (b) schematic diagram of the metal bar unit; (c) transmission spectra corresponding to different a; (d) dispersion characteristics of the grating and metal bar with different a

Fig. 3. Effects of different structural parameters on the transmission spectrum of grating-coupled meta-surface structures. (a) Transmission spectra with different a; (b) transmission spectra with different b; (c) transmission spectra with the simultaneous variation of a and b; (d) transmission spectra with different d

Fig. 4. Effects of structural parameters on the dispersion characteristics of periodic metal structures. (a) Dispersion characteristics with different a; (b) dispersion characteristics with different b; (c) dispersion characteristics with the simultaneous variation of a and b; (d) dispersion characteristics with different d

Fig. 5. (a) Electric field distribution of the SSP modes realized by the grating-coupled meta-surface structure. (b) Electric field and surface current distributions of the meta-surface structure at resonant frequency. The black arrows indicate the surface current direction

Fig. 6. Changes in transmissivity and the corresponding sensing sensitivity obtained by changing the ambient refractive index around the grating-coupled meta-surface. (a) Transmission spectra with different refractive indices; (b) the calculated sensing sensitivity