Abstract
Efficiently manipulating the polarization states of electromagnetic waves is of great importance for communication, imaging, and sensing. In this paper, we aim to control the circular polarization states, e.g., left-hand, or right-hand, for the bidirectional radiated waves utilizing a pair of back-to-back quarter-wave plates, which are integrated within an ultrathin cavity. As an example, a bidirectional circularly polarized wave with the same helicity in forward and backward is generated based on numerical analyses, and proved by experiments in microwave region. The proposed ultrathin back-to-back quarter-wave plates cavity can be adopted to higher frequencies, e.g., terahertz and mid-infrared ranges, with lower metallic conductivity. The proposed method exhibits the advantages of compact dimension and low-cost implementation in engineering the bidirectional polarization states of electromagnetic waves.
Highlights
Two aspects can illustrate the engineering values of this work: (i) Why do we need bidirectional CP waves with identical helicity? (ii) Why must we use single dielectric layer? For the first question, an important application using the proposed structure is the low-cost and temporal wireless relay systems in narrow channel environments, for example, coal mine and tunnel channels[9,10]
The polarization state of the back QWP is controlled in the same rule
For t = 0 (i.e., 0° phase), the electric field is concentrated in the shorter slot with a half wavelength mode and polarized along −45° with respect to the horizontal axis
Summary
Two aspects can illustrate the engineering values of this work: (i) Why do we need bidirectional CP waves with identical helicity? (ii) Why must we use single dielectric layer? For the first question, an important application using the proposed structure is the low-cost and temporal wireless relay systems in narrow channel environments, for example, coal mine and tunnel channels[9,10]. Two aspects can illustrate the engineering values of this work: (i) Why do we need bidirectional CP waves with identical helicity? (ii) Why must we use single dielectric layer? An important application using the proposed structure is the low-cost and temporal wireless relay systems in narrow channel environments, for example, coal mine and tunnel channels[9,10]. Bidirectional wave with the same helicity along the forward and backward directions is highly desired[9,10,16,17]. Single layered structure is more preferred for mass production from engineering point of view. Identical RCP wave for forward and back scattering or radiation in microwave are discussed as an example. A series of shorting wires are used to construct the metallic boundary condition as a cavity structure based on the low-cost PCB process[18]
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