Fig. 4: Simultaneous characterization of frequency and polarization state.

a The captured images on the focal plane at different frequencies under left and right circular polarization incidence. The inner and outer rings are respectively lightened as a function of the incident polarization state. b Intensity contrasts of the measured results at different frequencies. The values are on a logarithmic scale. The blue points represent the cases under the left circular polarization and the red ones for the right circular polarization state. c Relationship between the rotation angle of interfered spots and the incident frequency. The dashed purple line represents the analytical values. The blue background in (b) and (c) represents the designed operation bandwidth. LCP: left-handed circular polarization, RCP: right-handed circular polarization.