Polarization Detection of Terahertz Waves using All-Silicon Metasurfaces with Tightly Focusing Behavior

The manipulation of polarization states is reflected in the tailoring of light-matter interactions and has great applications in fundamental science. Nevertheless, the conventional polarization-separated detection behavior in the terahertz (THz) band is very challenging when applied to visualize the incident polarization state since its measurement requires sophisticated instrumentation. Here, the feasibility of its reconstruction of the full-Stokes parameter matrix in the THz band is explored by establishing an all-silicon decoupled metasurface based on the polarization multiplexing encoding technique. The pixelated focal spots gathered in the target plane allow us to employ more elaborate methods to extract the characteristic parameters of the incident polarization states. The resolvability of the THz polarization detection behavior with a single focal spot is further optimized benefiting from the longitudinal polarization component (E-z) generated by the tightly focused beam in the propagation direction. The capability of the E-z-component in determining the key parameters that compose the polarization ellipse is evaluated by predefining the random incident polarization on a standard Poincare sphere. Thus, the proposed scheme offers significant advantages in future THz communications, providing opportunities for ultra-compact, high-resolution full-Stokes polarization imaging and multidimensional information processing.