Broadband asymmetric transmission via angle-induced chirality enhancement in split ring resonators

Asymmetric Transmission (AT) allows direction-sensitive control of electromagnetic waves that is highly desirable in optical and microwave communication applications. In this paper, an angle-induced chirality enhancement approach is proposed through the introduction of angled splits in a split ring resonator based unit cell. This design approach, which enhances electromagnetic cross coupling, has been analytically and experimentally validated, yielding efficient and broadband AT operation with 27.1% fractional bandwidth from 14.8GHz to 19.4GHz. The AT magnitude of greater than 80% and transmission efficiency of 90% are achieved across the 4.6GHz bandwidth. These results when compared with recently published designs depict that the presented metasurface exhibits the most broadband AT in a bi-layered configuration with the thinnest reported form factor of 0.78mm in the microwave regime. The underlying physics of AT operation has been illustrated through analysis of surface currents and electric field distributions. More importantly, new insights into the effects of optical activity on the AT magnitude are presented. The proposed ultra-thin metasurface, operating in K and Ku bands, finds its application as a polarization-control device for modern radar and satellite communication systems.