Accurate Design of Low Backscattering Metasurface Using Iterative Fourier Transform Algorithm

Multiphysical Digital Coding Metamaterials for Independent Control of Broadband Electromagnetic and Acoustic Waves with a Large Variety of Functions

Fabricating materials with customized characteristics for both electromagnetic (EM) and acoustic waves remain a significant challenge using the current technology, since the demand of multiphysical manipulation requires a variety of material parameters that are hard to satisfy in nature. However, the emergence of artificially structured materials provides a new degree of freedom to tailor the wave-matter interactions in dual physical domains at the subwavelength scale. Here, a bifunctional digital coding metamaterial (MM) is proposed to engineer the propagation behaviors of EM and acoustic waves simultaneously and independently. Four kinds of rigid pillars with various material properties are employed to serve as 1-bit reflection-type digital meta-atoms with antiphase responses in both frequency spectra, thus offering the opportunities for independent field control as desired. The MM demonstrates excellent performance of scattering manipulations from 5700 to 8000 Hz in the acoustic region and 5.80-6.15 GHz in the microwave region. The bifunctional MM is verified through full-wave simulations and experimental measurements with good agreement, which stands out as a powerful tool for related applications in the future.

Independent control of harmonic amplitudes and phases via a time-domain digital coding metasurface

Harmonic manipulations are important for applications such as wireless communications, radar detection and biological monitoring. A general approach to tailor the harmonics involves the use of additional amplifiers and phase shifters for the precise control of harmonic amplitudes and phases after the mixing process; however, this approach leads to issues of high cost and system integration. Metasurfaces composed of a periodic array of subwavelength resonators provide additional degrees of freedom to realize customized responses to incident light and highlight the possibility for nonlinear control by taking advantage of time-domain properties. Here, we designed and experimentally characterized a reflective time-domain digital coding metasurface, with independent control of the harmonic amplitude and phase. As the reflection coefficient is dynamically modulated in a predefined way, a large conversion rate is observed from the carrier signal to the harmonic components, with magnitudes and phases that can be accurately and separately engineered. In addition, by encoding the reflection phases of the meta-atoms, beam scanning for multiple harmonics can be implemented via different digital coding sequences, thus removing the need for intricate phase-shift networks. This work paves the way for efficient harmonic control for applications in communications, radar, and related areas.