Tomorrow's Metamaterials: Manipulation of Electromagnetic Waves in Space, Time and Spacetime

Metamaterials represent one of the most vibrant fields of modern science and technology. They are generally dispersive structures in the direct and reciprocal space and time domains. Upon this consideration, I overview here a number of metamaterial innovations developed by colleagues and myself in the holistic framework of space and time dispersion engineering. Moreover, I provide some thoughts regarding the future perspectives of the area

General Mapping between Complex Spatial and Temporal Frequencies by Analytical Continuation

This paper introduces a general technique for inter-mapping the complex spatial frequency (or propagation constant) $\gamma=\alpha+j\beta$ and the temporal frequency $\omega = \omega_\text{r}+j\omega_\text{i}$ of an arbitrary electromagnetic structure. This technique, based on the analytic property of complex functions describing physical phenomena, invokes the analytic continuity theorem to assert the unicity of the mapping function, and find this function from known data within a restricted domain of its analycity by curve-fitting to a generic polynomial expansion. It is not only applicable to canonical problems admitting an analytical solution, but to \emph{any} problems, from eigen-mode or driven-mode full-wave simulation results. The proposed technique is demonstrated for several systems, namely an unbounded lossy medium, a dielectric-filled rectangular waveguide, a periodically-loaded transmission line, a one-dimensional photonic crystal and a series-fed patch (SFP) leaky-wave antenna (LWA), and it is validated either by analytical results or by full-wave simulated results.Comment: 11 pages, 11 figur

Nonreciprocal Phase Gradient Metasurface: Principle and Transistor Implementation

We introduce the concept of nonreciprocal nongyrotropic phase gradient metasurfaces. Such metasurfaces are based on bianisotropic phase shifting unit cells, with the required nonreciprocal and nongyrotropic characteristics. Moreover, we present a transistor-based implementation of a nonreciprocal phase shifting subwavelength unit cell. Finally, we demonstrate the concept with a simulation of a 6-port spatial circulator application

Design, Concepts and Applications of Electromagnetic Metasurfaces

The paper overviews our recent work on the synthesis of metasurfaces and related concepts and applications. The synthesis is based on generalized sheet transition conditions (GSTCs) with a bianisotropic surface susceptibility tensor model of the metasurface structure. We first place metasurfaces in a proper historical context and describe the GSTC technique with some fundamental susceptibility tensor considerations. Upon this basis, we next provide an in-depth development of our susceptibility-GSTC synthesis technique. Finally, we present five recent metasurface concepts and applications, which cover the topics of birefringent transformations, bianisotropic refraction, light emission enhancement, remote spatial processing and nonlinear second-harmonic generation

Time-Reversal Routing for Dispersion Code Multiple Access (DCMA) Communications

We present the modeling and characterization of a time-reversal routing dispersion code multiple access (TR-DCMA) system. We show that this system maintains the low complexity advantage of DCMA transceivers while offering dynamic adaptivity for practial communication scenarios. We first derive the mathematical model and explain operation principles of the system, and then characterize its interference, signal to interference ratio, and bit error probability characteristics