In this paper, the efficient transformation optics method has been utilized to design and analyze two-dimensional (2D) transparent cloaks, structures that can physically protect the devices inside but do not affect their electrical performances at all. The general and explicit expressions for the material parameters of the transformed space are derived. 2D transparent cloaks with arbitrarily conformal and nonconformal inner and outer boundaries and those working in gradually changing background and layered media are designed. Full-wave simulations combined with the Huygens’ principle are applied to validate the transparency of the cloaks. The simulation results under different circumstances demonstrate that the proposed method is correct and efficient. The work introduced here makes important progress in the theoretical design of the transparent cloak and expands the application of the transformation optics method.
Abstract-We propose a planar focusing antenna design, which has the same performance as its parabolic counterparts and can be realized using PEC-backed gradient index dielectrics. In this design, quasi-conformal transformation optics is first utilized to transform a parabolic surface into a planar one, then the anisotropy factor of the resultant material is minimized, and the material is approximately treated as isotropic. Examples with realizable material parameters are given, and the simulation results validate the design. The proposed method could be used to design planar focusing antennas with high directivity and similar devices. The idea can also be applied to new device designs in optics engineering.
Articles you may be interested inDesigning a square invisibility cloak using metamaterials made of stacked positive-negative index slabs Design of optical cloaks and illusion devices along a circumferential direction in curvilinear coordinatesWe propose a robust method to design arbitrarily directional cloaks by solving the Laplace's equation. The method is based on the orthogonality between light rays and eikonal curves. By employing the analogy between light rays and electric force lines, and the equivalence between eikonal curves and isopotential lines, the original problem in the geometrical optics is converted into a boundary value problem in electrostatics. Examples are given and the simulation results validate the design. The method can also be used to design other optical-transformation devices and be extended to solve three-dimensional problems. The medium parameters designed by the method are easily realized using metamaterials or normal materials, and hence, the method can find applications in the optical and microwave engineering.
Metasurfaces with spin‐selective reflection or transmission functions for circularly‐polarized (CP) incident waves have aroused researchers' great attention. However, current spin‐selective metasurface designs have yet to mature into a practical method due to the limitations of single operating band or inefficient phase modulation. Herein, a novel chiral meta‐atom is proposed, exhibiting spin‐selective absorption/reflection functions for dual‐orthogonal CP incident waves at three different operating bands. More significantly, the Pancharatnam–Berry phase theory is introduced at all working frequencies to generate a full 2π reflection phase modulation by rotating the chiral resonator, and the three distinct absorption bands remain almost constant with the rotation. Theoretical results indicate that high absorption can separately act on left‐handed or right‐handed CP incident waves at triple bands, and meanwhile, the other incident wave with different handedness is efficiently reflected without changing the handedness. As a proof of concept, two tri‐band meta‐devices with spin‐selective anomalous reflection and spin‐selective orbital angular momentum generating functions are designed and experimentally characterized, both of which exhibit excellent spin‐dependent bi‐functional performances at three different operating bands. The research results provide a promising route to realize spin‐selective meta‐devices with multi‐band operating modes in wireless communication systems and multispectral imaging and information encryption fields.
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