A frequency-tunable 90°-polarization rotation device using composite chiral metamaterials

The electromagnetic behaviors of the metamaterial can be artificially controlled by changing the effective permittivity of the nearby background medium. Utilizing this fantastic feature, an ultrathin and frequency-tunable polarization rotation device, which can achieve 90° polarization rotation for a linearly polarized incident wave, is constructed via the combination of a composite chiral metamaterial and two auxiliary dielectric slabs. It shows that the operating frequency of the resulting 90°-polarization rotation device can be continuously and reversibly tuned in a wide frequency range by mechanical means. The experimentally measured results are in agreement with the numerical values.