Broadband asymmetric transmission of linearly polarized electromagnetic waves based on chiral metamaterial

Abstract

The giant optical activity of chiral metamaterials (CMMs) holds great potential for tailoring the polarization state of an electromagnetic (EM) wave. In controlling the polarization state, the aspect of asymmetric transmission (AT), where a medium allows the EM radiation to pass through in one direction while restricting it in the opposite direction, adds additional degrees of freedom such as one-way channelling functionality. In this work, a CMM formed by a pair of mutually twisted slanted complementary metal strips is realized for broadband AT accompanied with cross-polarization (CP) conversion for linearly polarized EM waves. Numerically, the proposed ultra-thin (∼λ/42) CMM shows broadband AT from 8.58 GHz to 9.73 GHz (bandwidth of 1.15 GHz) accompanied with CP transmission magnitude greater than 0.9. The transmission and reflection spectra reveal the origin of the asymmetric transmission as the direction sensitive cross polarization conversion and anisotropic electric coupling occurring in the structure which is then elaborated with the surface current analysis and electric field distribution within the structure. An experiment is carried out to verify the broadband AT based CP conversion of the proposed CMM at microwave frequencies, and a reliable agreement between numerical and experimental results is obtained. Being ultra-thin, the reported broadband AT based CP conversion of the proposed CMM is useful for controlling radiation patterns in non-reciprocal EM devices and communication networks.

Angularly stable and broadband chiral metamaterial based design for asymmetric transmission of linearly polarized waves

“…The Jones transmission matrix T relates the complex amplitudes of the incidence and transmitted fields in terms of transmission coefficients. 23,39 T…”

“…However, these designs demonstrate wideband response only for normal incidence which significantly limited their use in practical applications. In 2018, Stephen et al 39 studied a bi‐layered chiral metamaterial (CMM) that exhibits a broad‐band (1.15 GHz bandwidth) AT for linearly polarized wave in microwave regime. The design shows angular stability to incidence angles up to 30°.…”

Advances and challenges in commercializing radiative cooling

“…Recent advances in non-reciprocal transmission have presented great opportunities for RC technology. Non-reciprocal transmission generally needs to break the Lorentz reciprocity, which can be achieved in many ways, that is, magneto-optical media [61e63], non-linear materials [64], photonic crystals [65], chiral structures [66,67], and metamaterials [68,69]. Most of these non-reciprocal transmission structures need additional energy input for spatial time modulation, and the modeling spectral range is narrow.…”

Experimental analysis and comparison between cross‐shaped metamaterial absorber and its complementary structure

“…Due to the excellent electromagnetic performance of electromagnetic metamaterials, MMs can be applied not only in many scientific fields, such as perfect lens, invisibility cloaking, and asymmetric transmission, but also can be achieved in different frequencies, from the microwave to the terahertz, or even visible light . With the development of nano‐materials and photonic fabrication technology, metadevices, defined as devices equipped with unique and useful functionalities that are realized by structuring of functional matter, have been the next research hotspot just recently.…”