arXiv subjects

Cheng-Wei Qiu

Publications and source records attributed to Cheng-Wei Qiu.

113 records · Page 7Linked to original sources

arXiv2009

Theory and optimization of transformation-based quadratic spherical cloaks

Based on the concept of the cloak generating function, we propose a numerical method to compute the invisibility performance of various quadratic spherical cloaks and obtain optimal invisibility results. A non-ideal discrete model is used to calculate and optimize the total scattering cross-sections of different profiles of the generating function. A bell-shaped quadratic spherical cloak is found to be the best candidate, which is further optimized by controlling design parameters involved. Such improved invisibility is steady even when the model is highly discretized.

physics.optics↗

arXiv2009

An inverse method of designing cylindrical cloaks without knowing coordinate transformation

An inverse way to define the parameters of ideal cylindrical cloaks is developed, in which the interconnection between the parameters is revealed for the first time without knowing a specific coordinate transformation. The required parameters are derived in terms of the integral form of cloaking generators, which is very general and allows us to examine the significance of the parametric profiles. The validity of such inverse way and the invisibility characteristics are presented in full-wave numerical simulation of plane wave scattering by cloaked cylinders.

physics.optics↗

arXiv2009

Achieving Invisibility of Homogeneous Radially Anisotropic Cylinders by Effective Medium Theory

In this paper, we establish the full-wave electromagnetic scattering theory to study the electromagnetic scattering from infinitely long cylinders with radially anisotropic coatings. We show that the total effective scattering width can be dramatically reduced by the suitable adjustment of the dielectric anisotropy of the shell, while it is not the case for tuning the dielectric anisotropy of the core. Furthermore, we could make the cylindrical objects invisible when both dielectric and magnetic anisotropies are adjusted. In the long wavelength limit, we develop effective medium theory to derive the effective isotropic permittivity and permeability for the anisotropic coated cylinders, and the invisibility radius ratio derived from the full-wave theory for small coated cylinders can be well described within the effective medium theory.

physics.optics↗

arXiv2009

Spherical cloaking using nonlinear transformations for improved segmentation into concentric isotropic coatings

Two novel classes of spherical invisibility cloaks based on nonlinear transformation have been studied. The cloaking characteristics are presented by segmenting the nonlinear transformation based spherical cloak into concentric isotropic homogeneous coatings. Detailed investigations of the optimal discretization (e.g., thickness control of each layer, nonlinear factor, etc.) are presented for both linear and nonlinear spherical cloaks and their effects on invisibility performance are also discussed. The cloaking properties and our choice of optimal segmentation are verified by the numerical simulation of not only near-field electric-field distribution but also the far-field radar cross section (RCS).

physics.optics↗

arXiv2008

Terahertz Metamaterials with Semiconductor Split-Ring Resonators for Magnetostatic Tunability

We studied a metasurface constituted as a periodic array of semiconductor split-ring resonators. The resonance frequencies of the metasurface excited by normally incident light were found to be continuously tunable in the terahertz regime through an external magnetostatic field of suitable orientation. As such metasurfaces can be assembled into 3D metamaterials, the foregoing conclusion also applies to metamaterials comprising semiconductor split-ring resonators.

cond-mat.mtrl-sci↗