# _Photonics_
## 3 Results and Discussion
Most of the energy is considered as reflected because the initially proposed structure is with a thin layer of copper; hence, the amplitudes of \(r_{u}\) and \(r_{v}\) are almost the same. Due to the asymmetry of the structure, the alleged polarization converter is to be considered as an anisotropic material, resulting in a phase difference of \(\Delta\varphi_{uv}=\varphi_{u}-\varphi_{v}=180^{\circ}\) between \(r_{u}\) and \(r_{v}\), as depicted in Figure 3. In this situation, the component \(E_{rv}\) will be opposite to \(E_{ir}\), and \(E_{ru}\) will be the same as \(E_{iu}\), resulting in the synthetic field \(E_{r}\) along the x-axis, which would validate the cross-polarization conversion. Further simulation results illustrated  
Figure 2: Simulation results of the proposed metasurface (**a**–**c**) co- and cross-polarization components \(r_{yy}\) and \(r_{xy}\); (**d**) polarization conversion ratio (PCR). The yellow subfigure in the corner of each graph (**a**–**c**) represents the design of unit cell used to calculate reflection curves. in Figure 4a,b justify the phase and amplitude conditions of \(r_{u}\) and \(r_{v}\). It can be seen that there is a 180\({}^{\circ}\) phase difference between the amplitudes from 13 GHz to 26 GHz, and that the amplitudes of these constituents are approximately equal to unity, agreeing to the broadband polarization conversion. The proposed polarization converter mechanism is as follows: When an electromagnetic wave comes into contact with a metasurface, electric and magnetic dipole moments are produced. The coupling of the magnetic and electric fields to the dipole moments is allowed by the bi-anisotropy of the structure as explained above. \(\left[ \begin{matrix}p\\ m\end{matrix} \right]=\left[ \begin{matrix}p_{ee}&p_{em}\\ p_{me}&p_{mm}\end{matrix} \right]\left[ \begin{matrix}E\\ H\end{matrix} \right]\), where \(p\) represents the electric dipole moments and \(m\) represents the magnetic dipole moments, respectively. \(p_{me}\) describes the magnetoelectric polarizability, and \(E,H\) represent the electric and magnetic field, respectively. The effective impedance of the metasurface is \(Z(\omega)=\sqrt{\mu(\omega)/\varepsilon(\omega)}\), where \(\varepsilon(\omega)\) and \(\mu(\omega)\) are the electric permittivity and magnetic permeability, respectively, while \(Z(\omega)\) is the surface impedance of the metasurface. The reflection coefficient reaches unity when the metasurface impedance is larger than the impedance of free space \(Z(\omega_{r})>Z_{\omega}\), and the surface acts like a high-impedance surface (HIS), where \(\omega_{r}\) represents the resonance frequency and \(Z_{\omega}=377\)\(\Omega\) is the free space impedance. In the case of a normal reflective surface, the reflected waves become out of phase, but here, incident electromagnetic waves will be reflected with unity amplitude and in-phase. As previously stated, the incoming wave polarization is turned by 90\({}^{\circ}\) when  
Figure 4: Simulation results of the proposed metasurface: (**a**) The reflected amplitudes of \(r_{u}\) and \(r_{v}\). (**b**) Phase difference. Figure 3: Scheme representing the decomposing of the orthogonal components. orthogonal components reflect at 180\({}^{\circ}\) or 0\({}^{\circ}\), and cross-polarization conversion results in such a case. It is deduced that this structure acts as a common reflector for one component and as a high-impedance structure for another. For a better understanding of the physical mechanism of the polarization conversion, the surface current distributions on the top metasurface and bottom layer are taken up for 13.78 GHz, and 26 GHz, as shown in Figure 5.  
It is depicted for 13.78 GHz that the surface currents on the top-most layer are antiparallel compared to ones on the bottom metallic layer. As shown in Figure 5a,b, this is indicative that the resonance at this frequency is magnetic in nature; therefore, the magnetic dipoles are the cause of the polarization conversion.