Dual-Band Circular Polarizer and Asymmetric Spectrum Filter Using Ultrathin Compact Chiral Metamaterial

A compact chiral metamaterial is proposed and comprehensively investigated that can achieve circularly polarized wave emission from linearly polarized incident wave (giant circular dichroism) over dual bands and near Diodelike asymmetric transmission of linearly polarized waves.The chiral metamaterial also features exceptionally strong optical activity.For verification, two proof-of-concept slab samples are designed, fabricated and measured at microwave frequencies.Numerical and experimental results agree well, indicating that the former dual-band circular polarizer features high conversion efficiency around 8.1 and 9.9 GHz in addition to large polarization extinction ratio of more than 16 dB, while the latter chiral sample enables the near 90% cross-polarization transmission in one direction and almost 10% transmission in the opposite direction.The block "meta-atom" that utilized to build the ultrathin CMM slab is less than λ 0 /6.73 evaluated at operating frequency.Good performances of the two chiral slabs with simple and compact package suggest promising applications in the circular polarizers (circulators) and transparent linear polarization transformers or spectrum filters (isolators) that need to be interpreted with other compact devices. INTRODUCTIONRecently, chiral metamaterials (CMMs) have attracted increasing attention from the microwave frequency band to optical spectrum