In physics, geometrical symmetry is a fundamental property of importance since it is associated with physical conservation. Here, we reveal an exceptional form of symmetry for a family of knots that are both chiral and three-dimensional (3D) rotationally symmetric about every axis of a standard Cartesian coordinate system. We call these unique knotted structures chiral balls. Moreover, chirality can bring about polarization transformation in electromagnetic waves. As a consequence of their 3D rotational symmetry, we further expect the polarization transformation performance of chiral balls to exhibit ultra-wide angle-independent behavior. Such a remarkable property has not been previously reported on in…

This chapter is organized as follows. In Section 7.2, innovative work on the optimization-enabled GST metasurfaces for sophisticated beam switching and control is highlighted. In Section 7.3, recent developments in the field of temporal artificial media are first reviewed, and then recent work on the time-varying anisotropic materials for complete polarization conversion is summarized. Finally, in Section 7.4, conclusions and a scope for future research are provided. Read more Lei Kang, Sawyer Campbell, Yuhao Wu, Jingwei Xu, Wending Mai, Eric Whiting, and Douglas H. Werner

This work introduces a new equivalent circuit generation method which can compute an accurate equivalent circuit representation for the known/measured impedance characteristics of antennas, which may assist in matching circuit design, non-Foster matching network design, and deep-learning antenna design. The method utilizes a modified Drude-Lorentz resonator representation inspired by optical material dispersion modeling to create multiple sub-circuits based on determined resonances in the impedance spectrum. Each computed sub-circuit is necessarily composed of physically realizable resistors, capacitors, and inductors, and they are connected in series to accurately reconstruct the device’s corresponding impedance characteristics over a specified region of interest. The process…

Optical activity is the ability of chiral materials to rotate linearly polarized electromagnetic waves. A knotted chiral metamolecule is introduced here that exhibits strong optical activity corresponding to a 90° polarization rotation of the incident waves. More importantly, the torus knot structure is intrinsically chiral and multifold axisymmetric. Consequently, the observed polarization rotation behavior is found to be independent of how the incident wave is polarized. The metamolecule is fabricated through selective laser melting and experimentally validated in the microwave spectrum. This work represents the first ever metamolecule to be reported that is intrinsically axisymmetric and capable of simultaneously exhibiting…

Various dispersion models can be expressed as special cases of the Generalized Dispersion Model (GDM), which is composed of a series of Pade polynomials. While important for its broad applicability, we found that some materials with Drude dispersive terms can be accurately modeled by mixing a 1st order Pade polynomial with an extra conductivity term. This conductivity term can be separated from the auxiliary differential equation (ADE). Therefore, the proposed mixed-order model can achieve the same accuracy with fewer unknowns, thus realizing higher computational efficiency and lower memory consumption. For examples, we derive the model parameters and corresponding numerical errors…

Prism DGTD simulation toolkit with GDM for pixelized metasurface This simulation package is the prism-based Discontinuous Galerkin Time Domain method with General Dispersion Model for analysis of gold pixelized metasurfaces. How to use it: Open "runme.m" in MATLAB. Modify the time span and the Geo matrix "A". The geometry is a 2-fold symmetric unit cell with a period of 400 nm. The unit cell can be patterned by several gold pixels, measures 50 nm × 50 nm × 20 nm. In order to add gold padding, one could input the number of padding, and then the index numbering. The index…