Multi-foci Geometry Metalens For Polarization Detection

The state of polarization (SoP) is one of the inherent properties of electromagnetic waves, and the important information they carry is indispensable in many applications. Conventional devices for measuring polarization states usually require complex measurement devices and cumbersome test procedures. Here, we present compact geometric phase metasurfaces consisting of a C-type cell in the millimeter-wave band, which can produce four focal points with different polarization states in the same focal plane. The intensity of the different focal points can be analyzed to determine the spin and ellipticity of the incident wave. Our device enables real-time polarization detection in the field of compact millimeter-wave polarization imaaing.