Cross polarization conversion based on a new chiral spiral slot structure in THz region

Triple-Band Polarization Angle Independent 90° Polarization Rotator Based on Fermat's Spiral Structure Planar Chiral Metamaterial

“…Generally, it is difficult to realize a linear polarization rotation up to 90 • with a high efficiency of crosspolarization conversion in previous CMM based on the mutual twisted resonator structures [7,14,15,[22][23][24][25][26][27][28]. Another CMM based on some longitudinal magnetic dipole coupling has been proposed to get strong rotatory strength [13,[34][35][36]. To achieve multi-band 90 • polarization rotation with a polarization angle independent response, a special PCMM structure with fourfold-rotational (C 4 ) symmetry is desirable to excite the multiple resonance mode for normal incident linear polarization wave.…”

“…The physical origin of the cross polarization conversion is illustrated by analyzing the surface current and electric field distributions of the unit-cell structure of the proposed PCMM. Compared with previous reported CMMs for polarization rotators [31][32][33][34][35][36], our design has some advantages: Firstly, our PCMM has an ultra-thin thickness and novel resonance mechanism. Secondly, the simple design of the PCMM has more operation frequencies in a single patterned metallic structure and is also polarization-insensitive for normal incident waves.…”

“…Essentially, these special CMMs structures for polarization rotations or conversions with high efficiency mainly originate from their extrinsic chirality induced by the EM coupling effects. These CMMs structures have been proposed to obtain cross polarization waves in transmission, which can exhibit cross polarization conversion or giant optical activity by 90 • linear polarization rotation [32][33][34][35][36]. These CMMs structures are usually constructed by bi-layered or triple-layered enantiomeric metallic patterns sandwiched with dielectric substrates [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

“…Recently, a CMM based on twisted electric field coupled resonators was proposed by Shi et al, which can realize a dual-band 90 • polarization rotation with polarization angle insensitive in microwave region [35]. Then, a new CMM based on a spiral slot structure was proposed by Tang et al, and dual-band cross-polarization conversion could be realized in terahertz region [36]. However, the transmission coefficient of cross-polarization is relatively small, and current designs of CMMs are mainly concentrated on dual bands, which could hamper their practical engineering applications.…”

Exhibition of polarization conversions with asymmetric transmission theory, natural like chiral, artificial chiral nihility and retrieval studies for K- and C-band radar applications

“…Therefore, they can be designed for any desired frequency regimes and have potential applications depending on manufacturing capability. They are represented with the chirality parameter κ, which can be found as κ = (n R − n L )/2, where n R and n L are the refractive index of the right and left circularly polarized (RCP and LCP) waves, respectively [4][5][6][7][8][9][10][11][12][13]. There are many chiral MTM studies in the literature, but unlike the others, in this study, we present simple design (π -shaped), easy fabrication, large optical activity, circular dichroism, chiral nihility and constant value of chirality in a wide band by using two π -shaped periodic structures.…”