Metamaterials (MMs) have already achieved wide applications in academia and industry. The traditional design approach for MMs highly relies on full-wave numerical simulations and trial-and-error methods. It is time-consuming and laborious to obtain the optimal design parameters. Recently, extensive researches have shown advantages and superiority of the deep learning method in solving non-intuitive problem. Several attempts have been made to demonstrate Artificial Intelligence (AI) usage in the electromagnetic field. In this paper, a target-driven method empowered by deep learning to realize customized metamaterial absorber (MMA) design has been proposed and demonstrated numerically. Unlike previous deep-learning-based design methods for MMs which directly use the spectrum response to generate the MM’s design parameters, this method takes the frequency domain response of the absorber as the intermediary bridge to establish the mapping between MMAs geometry/material parameters and customized figure-of-merits. The proposed design framework greatly simplified the design process of MMAs, and it can also be generalized to realize automatic inverse design for other kinds of metasurfaces.

In this paper, a broadband metamaterial absorber with a fractional bandwidth of 126.88% was presented. The characteristic mode theory was used to guide the design of the absorber. According to the analysis of characteristic mode and characteristic current, the resistance value of resistive films can be determined. The different modal information obtained through parameter changes can also better guide the design of the absorber. To study its operation mechanism, the equivalent impedance and surface current distribution of the proposed absorber have been analyzed. The final simulation and measurement results show that the proposed absorber has a wide absorbing bandwidth which is from 3.21 to 14.35 GHz, and the absorptivity is greater than 90%, covering the S, C, X, and Ku bands. In addition, for TE and TM polarization, it can achieve an absorptivity of more than 85% at 45° oblique incident and has good angular stability. Hence, the absorber has great potential applications in the field of electromagnetic stealth technology and Radar Cross Section reduction.

The scattering enhancement technique has shown prominent potential in various regimes such as satellite communication, Radar Cross Section (RCS) camouflage, and remote sensing. Currently, the scattering enhancement devices based on the metasurface have shown advantages in light weight and better performance. These metasurfaces always possess complex structure, it is hard to achieve through the tradition trial-and-error method which relies on the full-wave numerical simulation. In this paper, a new method combining the machine learning and the evolution optimization algorithm is proposed to design the metasurface retroreflector (MRF) for arbitrary direction incident wave. In this method, a predicting model and a generative inverse design model are constructed and trained, the predicting model is used to evaluate the fitness of each offspring in the genetic algorithm (GA), the generative model is used to initialize the first offspring of the GA by inverse generate the MRF based on the requirements of the designer. With the assistance of these two machine learning models, the evolution optimization algorithm is employed to find the optimal design of the MRF. This approach enables automatic solution of electromagnetic inverse design problems and opens the way to facilitate the optimization of other metadevices.

Generating and manipulating Dirac points in artificial atomic crystals has received attention, especially in photonic systems due to their ease of implementation. In this Letter, we propose a two-dimensional photonic crystal made of a Kekulé lattice of pure dielectrics, where the internal rotation of cylindrical pillars induces optical Dirac-degeneracy breaking. Our calculated dispersion reveals that the synchronized rotation reverses bands and switches parity as well so as to induce a topological phase transition. Our simulation demonstrates that such topologically protected edge states can achieve robust transmission in defect waveguides under deformation, and therefore provides a pragmatically tunable scheme to achieve reconfigurable topological phases.

In this paper, we theoretically and experimentally demonstrate a three-dimensional metamaterial that can motivate electromagnetic induced transparency (EIT) by using circular polarized wave as stimulations. The unit cell consists of a pair of metallic strips printed on both sides of the printed circuit board (PCB), where a conductive cylinder junction is used to connect the metal strips by drilling a hole inside the substrate. When a right circularly polarized wave is incident, destructive interference is excited between meta-atoms of the 3D structure, the transmission spectrum demonstrates a sharp transparency window. A coupled oscillator model and an electrical equivalent circuit model are applied to quantitatively and qualitatively analyze the coupling mechanism in the EIT-like metamaterial. Analysis in detail shows the EIT window’s amplitude and frequency are modulated by changing the degree of symmetry breaking. The proposed metamaterial may achieve potential applications in developing chiral slow light devices.

A compact dual-polarized base-station antenna with filtering characteristics is proposed in this letter. The antenna is composed of a reflector, two balun structures, and two orthogonal half-wavelength radiation arms. The radiation arm mainly consists of multiple transmission lines of different widths, which can be equated to inductance or capacitance. The elaborately designed radiation arm not only ensures a wideband operation but also helps to achieve low-pass filtering characteristics, without using an extra parasitic structure. For demonstration, a $\pm 45^\circ$ dual-band dual-polarized antenna array operating at 690–960 MHz and 1710–2690 MHz are fabricated and measured. The implemented array (690–960MHz) achieves stable half-power beamwidth (HPBW) of 65 $^\circ$ $\pm$ 10 $^\circ$ and polarization isolation of 27 dB. Due to the filtering performance of the proposed antenna, stable high gain (17.5 $\pm$ 1 dBi) and HPBW of 65 $^\circ$ $\pm$ 6 $^\circ$ also can be realized at 1710–2690 MHz. The proposed antenna is suitable for the base-station application.