Terahertz all-silicon metasurfaces with off-axis bifocal characteristics for polarization detection.

Functional devices for terahertz (THz) polarization detection in transmission mode are highly desired in integrated applications, but traditional polarization measurement systems are bulky and highly cost. The combination between all-silicon metasurfaces and focused beams carrying polarization information has offered a new opportunity for miniaturized polarization detection behavior. Here, we investigate and experimentally demonstrate a new scheme for realizing efficiently miniaturized polarization detection behavior based on the polarization multiplexing encoding technique. The full-Stokes parameter matrix of the incident polarization state can be reconstructed in a single snapshot by using a microprobe to record, pixel by pixel, the complex amplitude information contained in a pre-designed plane. Subsequently, the polarization detection capability of the proposed design principle is evaluated using random polarization states defined on the surface of a standard Poincaré sphere (PS). Such a scheme offers potential applications for the development of compact photonic meta-platforms for polarization detection in transmission mode, being highly favored in polarization high-resolution imaging, remote sensing, and THz communications.