Fig. 1. Schematic diagram of the metasurface which can independently control the phase of two circularly polarized incident waves. The cells are cross-shaped elliptical columns; both the cells and the substrate are made of high-resistance silicon.

Fig. 2. Simulation and results selection of the geometric parameters of meta-atoms. (a) Schematic diagram of the units. (b)–(e) The transmission amplitudes and phase shifts of the silicon cylinder for x- and y-polarized terahertz waves with different values of Lx and Ly. (f), (g) The selected 64 sets of Ly and Lx values, in which the phases are divided into eight values at intervals of 45 deg.

Fig. 3. Phase design of the metasurface with circular dichroism-like effect consists of 140×140 units. (a) The phase matrices consist of equal elements or pseudorandom numbers (submatrix with equal elements). (b) The phase distributions corresponding to the phase matrices (in π/4). (c)–(f) Far-field patterns of the metasurfaces with phase distributions of a constant or a random number matrix.

Fig. 4. Morphology characterization and transmission spectrum of the metasurface. (a) Optical photograph and scanning electron microscope (SEM) images of sample 1. (b) Simulated two-dimensional electric field and phase distributions of the transmitted LCP and RCP waves. (c) Terahertz polarization measurement time-domain spectroscopy system. (d) Simulation results of the TCD spectrum for metasurfaces with different numbers of units. (e)–(j) Experiment results of the linear and circular polarization transmission coefficients and TCD spectra.

Fig. 5. Spin-selective wavefront control of transmitted terahertz wave using the proposed metasurface. (a) Optical photograph and SEM images of sample 2. (b) Experimental setup of sample 2. (c)–(j) Simulations and measured results of the two-dimensional electric field and phase distributions.