Fig. 1. Schematic of the proposed all-dielectric metasurface for terahertz polarization detection. (a) For arbitrarily polarized wave incidence, the incident polarization state can be obtained by analyzing the mode of the transmitted field. (b) Diagram of a Poincaré sphere; arbitrary polarization state on the spherical surface can be represented using three coordinates (2α,2ψ,2ε). (c) The mode analysis of the transmitted field mainly consists of three parts: first, the decomposition of the mode purity of the transmitted vortex field; second, the orientation angle of the transmitted x-polarized field; third, the phase distribution of the transmitted x-polarized component.

Fig. 2. Characterization of the used meta-atoms. (a) Diagram of the anisotropic rectangular pillar. (b) Simulated transmission amplitudes (blue) and phase shifts (red) of the selected 15 meta-atoms under the x- and y-polarized incidences. (c) Spatial diagram of the selected meta-atoms for realizing spin-decoupling. For each row of eight meta-atoms, they have the same phase shifts when the left-handed circularly polarized light is incident; for each column of eight meta-atoms, they have the same phase shifts when the incident wave is right-handed circularly polarized.

Fig. 3. Characterization of the proposed all-dielectric metasurface for polarization detection: the trajectory of the incident wave’s polarization state follows the meridian direction, transitioning from x-polarization to right-handed circular polarization, and then to y-polarization. (a)–(g) Intensity distributions, mode purity spectra of the transmitted vortex fields, and comparisons of polarization ellipses between the incident polarization states (blue) and the detected polarization states (red). (h) Representation as points on the Poincaré sphere of the input states (spheres) and the corresponding states identified by the metasurface (hexagrams). (i) Comparison of theoretical angles of amplitude ratio and obtained angles through simulations.

Fig. 4. Characterization of the proposed all-dielectric metasurface for polarization detection: the trajectory of the incident wave’s polarization state follows the equatorial direction, from −45°-linear polarization through x-polarization, and then to 45°-linear polarization. (a) Representation as points on the Poincaré sphere of the input states (spheres) and the corresponding states identified by the metasurface (hexagrams). (b) Full-Stokes parameters of the incident polarization states and the corresponding states identified by the proposed metasurface. (c) Intensity distributions of the transmitted x-polarized field. (d) Polarization ellipses of the incident polarization states (blue) and the detected polarization states (red).

Fig. 5. Characterization of the proposed all-dielectric metasurface for polarization detection: five arbitrarily selected elliptical polarization states. (a) Intensity distributions of the transmitted x-polarized field. The insets are corresponding phase distributions. (b) Polarization ellipses of the incident polarization states and the detected polarization states. (c) Representation as points on the Poincaré sphere of the input states (hexagrams) and the corresponding states identified by the metasurface (*). (d) Full-Stokes parameters of the incident polarization states and the corresponding states identified by the proposed metasurface.

Fig. 6. Experimental characterization of the proposed all-dielectric metasurface for terahertz polarization detection. (a) SEM image of fabricated metasurface. The inset is a partially enlarged side view. (b) Full-Stokes parameters of the incident polarization states and the corresponding states experimentally identified by the proposed polarization detection scheme. (c) Intensity distributions, phase distributions, and comparisons of polarization ellipses between the incident polarization states (blue) and the measured polarization states (magenta).

Fig. 7. Transmitted fields of the proposed all-dielectric metasurface under left-handed and right-handed circularly polarized incidences. (a) Intensity distribution of the transmitted right-handed circularly polarized channel under left-handed circularly polarized incidence. The inset is corresponding phase distribution. (b) Intensity distribution of the transmitted left-handed circularly polarized channel under right-handed circularly polarized incidence. The inset is corresponding phase distribution.