Tunable symmetric and asymmetric resonances in an asymmetrical split-ring metamaterial

Abstract

We demonstrate the coexistence of two tunable symmetric and asymmetric resonances in a metamaterial composed of asymmetrical split-rings (ASRs) patterned on a dielectric layer numerically and experimentally. The full-wave simulation and measurement results demonstrate that the metamaterial reveals a symmetric cross-polarization transmission band with a ripple-free peak and asymmetric co-polarization transmission bands characterized by trapped-mode resonances. Both symmetric and asymmetric resonances can be easily tuned via the incident angle of electromagnetic waves. The resonant excitation and coupling of the electric and magnetic dipole moments contribute to the conversion of two orthogonal linear polarizations. The ASR metamaterial shows a directionally asymmetric transmission for both linearly and circularly polarized waves for large angles of incidence. The proposed ASR metamaterial is of importance to develop novel metamaterial-based devices.

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

“…However, the cross-polarized conversion in above literature was insufficient. This is particularly true for the weak crosspolarization transmission(less than 0.3) of the asymmetric SRR whose element size reaches λ 0 /3.3 at the resonance [14]. To realize a Diodelike asymmetric transmission, namely unity transmission of certain linear polarization in one direction while zero transmission in the opposite direction, electromagnetic wave tuning was suggested to be accompanied with the magnetoelectric coupling [15].…”

“…Asymmetric transmission for linear polarization is unusual and appealing polarization functionalities studied in recent years [11][12][13][14][15]. In [11], a thin structure composed of three-dimensional metaatoms allowing asymmetric transmission for an arbitrary including linear polarization of the incident electromagnetic wave was proposed without any rotational symmetry.…”

“…Afterwards, theoretical prediction and experimental realization on asymmetric transmission for linear polarization only were continuously reported by using gammadion structure [11] and SRR structure [12,13], respectively. In [14], the directionally asymmetric transmission of linearly and circularly polarized waves was suggested to be manipulated via angles of incidence. However, the cross-polarized conversion in above literature was insufficient.…”

“…These drawbacks make them not good candidates in this area. An asymmetry was recently introduced in both arc and gaps so that the resulting metamaterial has no line of mirror symmetry [10,14,30], enabling the asymmetric transmission of circularly polarized wave, however, this leads to exceptionally large meta-atoms.…”

“…due to their unique electromagnetic (EM) properties and a wider set of functionalities such as giant optical activity [1], elliptical or circular dichroism [2], giant gyrotropy [3], negative refraction without simultaneous negative permittivity and permeability [4][5][6][7][8][9], and asymmetric transmission [10][11][12][13][14][15], etc. The unusual polarization functionalities and chirality not found in natural medium arise from the magneto-electric cross coupling of chiral structures due to their bianisotropy and lack of any mirror symmetry.…”