Compact e-shape metasurface with dual-band circular polarization conversion

• A novel compact metasurface is proposed, which is not only extremely thin, but also very small.
• With giant circular dichroism effect and balanced optical activity at two resonant frequencies.
• The effective refractive index is negative in the vicinity of the resonant frequencies .

Double-band circular polarization conversion based on novel e-shape resonators is proposed and studied both numerically and experimentally. Both the simulated results and experimental results are in good agreement. At two resonant frequencies, i.e., 11.65 GHz and 13.02 GHz, the incident y-direction linearly polarized wave can be transformed into right- and left-handed circularly polarized waves, respectively. The proposed structure can transmit a nearly pure circularly polarized wave, with a polarization extinction ratio of greater than 30 dB. Moreover, the metasurface is compact with simple geometry, which is not only extremely thin in the propagating direction but also very small in the transverse direction. The retrieval results reveal that the effective refractive index of the e-shape structure is nearly negative in the vicinity of resonant frequencies. The surface current distributions are investigated to illustrate the polarization transformation mechanism. We also analyze the influence of several main geometric parameters for regulating the polarization properties. The proposed e-shape structure is promising for use in the design of polarization control devices.