Figure 4. A coherent polarization rotator based on intrinsic 3D chirality.

(a) Unit cell and fragment of the metamaterial array consisting of pairs of mutually twisted metal patterns spaced by a dielectric substrate of 1.6 mm thickness with the incident polarization marked by a white double arrow. (b) Transmission characteristics of the metamaterial at normal 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. The inset shows the x-component of the current density at the 4.9 GHz resonance. (c) Coherent control of these optical properties at close to normal incidence (θ = 13°) with an additional y-polarized control beam as a function of the phase difference α between the control and signal beams. Insets show the x-component of the current density at the 10.7 GHz resonance for phases α = 0° and 180°. (d) The same optical properties for a selected frequency of 4.91 GHz, where the metamaterial behaves as a coherent polarization rotator which can rotate the polarization azimuth continuously over the full 180°. Solid black lines and color maps show experimental data, while solid gray lines correspond to simulations. The azimuth rotation and ellipticity data shown in the last two rows have been reprinted with permission from Ref. 30. Copyright 2014, AIP Publishing LLC.