Fig. 1. Output polarization states shown on a Poincaré sphere for (a) previously realized metasurfaces that split polarizations into pairwise orthogonal states between different outputs (1 and 4, 2 and 3) and (b) the proposed metasurface, which achieves spatially uniform polarization across several outputs. (c) A schematic depicting a metasurface which converts an unpolarized input into $N$ outputs with identical polarization states $|\psi ⟩$. (d) The permissible transmitted power of an ideal polarizer for a different number of outputs. The red markers show the allowed transmission of individual output channels, and the blue markers show the maximum total transmission of all output channels.

Fig. 2. (a) Illustration of the dual-output polarizing metasurface. (b) Operating scheme of the metasurface in transmission, with an incident angle of $\alpha =45\mathrm{deg}$ and first-order diffraction angle of $\beta =68\mathrm{deg}$. (c) Final metasurface design of the single unit cell, with a period 950 nm along both directions. The shaded region represents silicon, and the void represents air. (d) Electric field intensity enhancement for incident $|H⟩$ polarization, and (e) $|V⟩$ polarization. These have the same unit cell dimensions as (c). (f) Predicted transmitted power, and (g) extinction ratio of the diagonal linear polarization for each diffraction order.

Fig. 3. (a) Top-down and (b) tilted SEM images of the fabricated metasurface. (c) Simplified experimental setup. The source transmits through the metasurface, which diffracts the beam into two orders. Each arm analyses the diagonal polarization before reaching the detector. (d) Measured transmitted power, and (e) extinction ratio of the diagonal polarization for each diffraction order for an incident angle $\alpha =45\mathrm{deg}$.

Fig. 4. (a) Operating principle of a three-output metasurface polarizer. The incident beam is normal, and $\alpha =75\mathrm{deg}$. (b) The binarized metasurface pattern, with shaded regions representing silicon and the void representing air. (c) Transmittance of desired vertical polarization versus wavelength. (d) Extinction ratio of combined vertical to horizontal polarization.