Abstract
Polarization control of electromagnetic wave is very important in many fields. Here, we propose an active meta-mirror to dynamically manipulate electromagnetic polarization state at a broad band. This meta-mirror is composed of a double-layered metallic pattern backed by a metallic flat plate, and the active elements of PIN diodes are integrated into the meta-atom to control the reflection phase difference between two orthogonal polarization modes. Through switching the operating state of the PIN diodes, the meta-mirror is expected to achieve three polarization states which are left-handed, right-handed circular polarizations and linear polarization, respectively. We fabricated this active meta-mirror and validated its polarization conversion performance by measurement. The linearly polarized incident wave can be dynamically converted to right-handed or left-handed circular polarization in the frequency range between 3.4 and 8.8 GHz with the average loss of 1 dB. Furthermore, it also can keep its initial linear polarization state.
Highlights
Where k is the wave vector in free space and d is the thickness of dielectric spacer. i =x, y represent the electric field polarized along the x- and y-direction, respectively
Zi(ω) indicates the surface impedance of the meta-mirror, and Z0 = 377 Ω is the impedance of free space. Both φxx and φyy are frequency dependent, and the transformation of LP wave to LHCP or RHCP wave would be produced assuming that Δφ(ω) =φxx(ω) −φyy(ω) = 90° or −90° and no material loss is generated
The active elements of PIN diodes are loaded on the gaps of the cross metallic strips along both x- and y- directions where they are independently controlled by the bias voltage, so that we can dynamically tune the phase difference between these two orthogonal directions
Summary
The proposed meta-mirror is generally composed of an anisotropic metallic pattern and a metallic flat plate with a dielectric spacer between them. As it shows, a strong absorption phenomenon is produced in the x- polarization at the frequency of 7.594 GHz, which means that there is almost no reflection wave energy. The designed meta-mirror has been experimentally verified to have three polarization states which can be dynamically controlled as required
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