Fig. 1. Schematic of the VO2-based metamaterial photodetector with active color rendering.

Fig. 2. Calculated reflection spectra of the VO2-based metamaterial absorber with phase transitions from the insulating state to the metallic state at tVO2=20  nm, tinsulator=5  nm, (a) p=470  nm, FF=0.3, (b) p=440  nm, FF=0.5, and (c) p=260  nm, FF=0.6. The solid line represents the reflective spectrum at the insulating state, while the dashed line stands for the spectrum at the metallic state. (d) The calculated CIE 1931 chromaticity diagram of the corresponding spectra showing in (a)–(c). The red triangle formed by the red squares as the triangle vertices shows the color gamut when VO2 is at the insulating state, while the blue triangle formed by the blue circles represents the color space at the metallic state.

Fig. 3. (a) Reflection spectra of the VO2-based metamaterial absorbers at the insulating and metallic states when the period varies from 220 to 700 nm, with the dashed trend lines tracing the location of similar resonant modes. Filling factor FF, tVO2, and tinsulator are fixed at 0.5, 20 nm, and 5 nm, respectively. (b), (c) Contour maps of the reflection spectra in (a) that are normalized to the area of the unit cell with the insulating and metallic states, respectively.

Fig. 4. Calculated reflection spectra with different filling factors ranging from 0.3 to 0.7 in the (a) x and (b) y directions at the insulating state with the associated filling factor FF=0.5 in the y and x directions. p, tVO2, and tinsulator are fixed at 500, 20, and 5 nm, respectively. “None” means there is no silver nanoparticle in the structure. The normal polarization illumination light is along the x direction. (c)–(e) The magnetic field distributions at resonant wavelengths of 440, 665, and 2500 nm with period p=500  nm, respectively. The filling factor FF in both the x and y directions is fixed at 0.5. The rest of the parameters are the same as the insulating ones in Fig. 3(a).

Fig. 5. Calculated colors evolve with different periods and filling factors at the insulating state and the metallic state under D65 illuminations. The period varies from 260 to 580 nm, and the filling factor changes from 0.3 to 0.6.