Figure 5. A coherent polarization rotator based on extrinsic 3D chirality.

(a) Unit cell and fragment of the metamaterial array consisting of asymmetrically split ring apertures in an aluminum sheet with the incident polarization marked by a white double arrow. (b) Transmission characteristics of the metamaterial for 30° oblique incidence of a y-polarized signal beam in terms of y-to-y intensity transmission, y-to-x intensity conversion, azimuth rotation and ellipticity angle of the detected beam. (c) Coherent control of these optical properties with an additional y-polarized control beam as a function of the phase difference α between the control and signal beams. (d) The same optical properties for a selected frequency of 9.27 GHz, where the metamaterial behaves as a coherent polarization rotator which can rotate the polarization azimuth continuously over the full 180° range while the ellipticity angle remains small (within ±15°). Solid black lines and color maps show experimental data, while solid gray lines correspond to simulations.