Fig. 1. Schematic diagram of the designed OTMMA. The geometrical parameters in the inset are t1 =2  mm, t2 =1  mm, t3 =1  mm, p=15  mm, l1 =11.39  mm, d=1.1  mm, w1 =3  mm, w2 =6.21  mm, g=0.5  mm, e=1  mm, l2 =1.73  mm, and l3 =11.26  mm.

Fig. 2. Numerical results of a metamaterial absorber. (a) Reflectance/transmittance/absorptance spectra under normal incidence. (b) Reflectance over varied polarization angles under normal incidence. Reflectance over various incident angles under (c) TE-polarized and (d) TM-polarized waves.

Fig. 3. Generation process of the Thiessen polygon mesh. (a) Generation of random discrete points. (b) Generation of the Delaunay triangular mesh grid. (c) Generation of the circumcenter of each triangle. (d) Generation of the Thiessen polygon mesh grid.

Fig. 4. (a) Schematic diagram of an optical system with a mesh window. PSF of the optical system (b) without a metal mesh, (c) with a square metal mesh, and (d) with an OTMMA. Simulated MTF curves of the optical system with (e) 0° and (f) 5° FOVs, respectively. The wavelength of the incident light is 532 nm, the focal length is f=200  mm, the distance from the window to the lens is 10 mm, and the aperture size of the optical system is 10 mm.

Fig. 5. (a) Micrograph of the fabricated TPMM; (b) and (c) scanning electron microscope (SEM) images of the TPMM.

Fig. 6. (a) Experimental setup for measuring reflectance. (b) Experimental setup for measuring SE. (c) Measured reflectance of the OTMMA under TE- and TM-polarized EM waves with the incidence angle ranging from 10° to 45°. (d) Measured SE of the OTMMA under TE- and TM-polarized EM waves.

Fig. 7. (a) Outdoor image of the fabricated OTMMA. (b) Measured optical transmittance of the OTMMA and quartz substrate.

Fig. 8. Schematic of an optical system with the OTMMA window.

Fig. 9. Schematic of micro pixel discretization of the metasurface and TPMM.

Fig. 10. Measured visible transmission of quartz with and without ITO film.

Fig. 11. (a), (b) and (c) Current distribution on metasurfaces 1, 2 and 3, respectively. (d), (e) and (f) Electric field on metasurfaces 1, 2, and 3, respectively.

Fig. 12. (a) Simulated reflectance of the OTMMA when surface resistance of the ITO metasurface is different. (b) Average absorptance of the OTMMA from 8 to 26.5 GHz versus surface resistance of the ITO metasurface.

Fig. 13. Equivalent circuit model of the OTMMA.

Fig. 14. Calculated input impedance of the OTMMA.