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…

Planar photonics technology is expected to facilitate new physics and enhanced functionality for a new generation of disruptive optical devices. To analyze such planar optical metasurfaces efficiently, we propose a prismatic discontinuous Galerkin time domain (DGTD) method with a generalized dispersive material (GDM) model to conduct the full-wave electromagnetic simulation of planar photonic nanostructures. Prism-based DGTD allows for triangular prismatic space discretization, which is optimal for planar geometries. In order to achieve an accurate universal model for arbitrary dispersive materials, the GDM model is integrated within the prism-based DGTD. As an advantage of prismatic spatial discretization, the prism-based DGTD with…

Chiral mirrors are a class of metamaterials that reflect circularly polarized light of a certain helicity in a handedness-preserving manner, while absorbing circular polarization of the opposite handedness. However, most absorbing chiral mirrors operate only in a narrow frequency band, as limited by the causality principle. Instead of absorbing the undesired waveform, here we propose a transparent chiral mirror that allows undesired waves to pass through. In particular, the handedness-preserving band of the transparent chiral mirror is free of the causality limit, thus enabling broadband functionality. Furthermore, since electromagnetic waves outside the handedness-preserving band may transmit through the proposed chiral…