Fig. 1. PIT structure and simulated transmission spectrum. (a) Schematic of the PIT structure detailing the unit structure geometric parameters: P_x = 80 µm, P_y = 120 µm, d = 7 µm, and g = 32 µm. The dimensions of the CW are 90 µm in length and 5 µm in width. For the SRRs, both the length and width are 29 µm, and the photosensitive silicon features sizes of 5 µm in both length and width. (b) The simulated transmission spectra of the three metasurface samples, including a PIT array (blue), a CW array (red), and an SRR array (orange).

Fig. 2. Active modulation of the PIT window through conductivity σ regulation. A comparative analysis of the simulated results and theoretical fittings in the PIT structure transmission spectrum at varied conductivity. Conductivity σ values are (a) 0, (b) 500, (c) 1500, (d) 3000, (e) 5000, and (f) 10,000 S/m, respectively. The red curve represents the simulated transmission spectrum, while the blue dotted line illustrates the fitting results obtained using the Lorentz resonator model.

Fig. 3. Electric distribution of the z-component on the PIT structure under varying conductivities. (a) Illustrates the electric z-distribution at a conductivity of 0 S/m, (b) depicts the distribution at a conductivity of 5000 S/m, and (c) presents the distribution when the conductivity reaches 10,000 S/m.

Fig. 4. Variations in the fitting parameters relative to conductivity σ, analyzing the transmission spectrum of the PIT structure. The fitting focuses on the behavior of the key parameters (δ, γ₁, γ₂, and κ) as they respond to changes in conductivity σ across different values.

Fig. 5. Variations in the group delay with respect to conductivity and parameters d and g. (a) Illustrates the group delay extracted from the transmission spectrum at various conductivity values. (b) Details the group delay as a function of the parameters d and g, specifically when the conductivity is maintained at 0 and 1500 S/m.

Fig. 6. Fitting parameters in relation to parameters d and g. (a) and (b), respectively, present the variations in the fitting parameters of the transmission spectrum corresponding to changes in the parameters d and g.

Fig. 7. Variations in Δf relative to parameters d and g under diverse conductivities. (a) and (b), respectively, illustrate the response curves of parameters d and g at conductivity values of 0 and 1500 S/m. (c) provides a magnified view of the curve within the blue-shaded region shown in (a) and (b).