Information metamaterials – from effective media to real-time information processing systems

Abstract

Metamaterials have been characterized by effective medium parameters over the past decades due to the subwavelength nature of meta-atoms. Once the metamaterials are fabricated, their functions become fixed or tunable. Recently, the concept of digital metamaterials has been introduced, in which, for instance, the constitutive 1-bit meta-atom is digitalized as “0” or “1” corresponding to two opposite electromagnetic (EM) responses. The digital metamaterials set up a bridge between the physical world and the information world. More interestingly, when the digital meta-atom is programmable, a single metamaterial can be used to realize different functions when programmed with different coding sequences. Moreover, as the states of programmable meta-atoms can be quickly switched, it enables the wave-based information coding and processing on the physical level of metamaterials in real time. For these reasons, we prefer to call digital metamaterials with programmable meta-atoms as “information metamaterials.” In this review article, we introduce two basic principles for information metamaterials: Shannon entropy on metamaterials to measure the information capacity quantitatively and digital convolution on metamaterials to manipulate the beam steering. Afterwards, two proof-of-concept imaging systems based on information metamaterials, i.e. programmable hologram and programmable imager, are presented, showing more powerful abilities than the traditional counterparts. Furthermore, we discuss the time-modulated information metamaterial that enables efficient and accurate manipulations of spectral harmonic distributions and brings new physical phenomena such as frequency cloaking and velocity illusion. As a relevant application of time-modulated information metamaterials, we propose a novel architecture of wireless communication, which simplifies the modern wireless communication system. Finally, the future trends of information metamaterials are predicted.

A Thin Self‐Feeding Janus Metasurface for Manipulating Incident Waves and Emitting Radiation Waves Simultaneously

“…[ 31–39 ] Recently, a number of efforts have been devoted to the reconfigurable multifunctional metasurfaces by hybridizing metasurfaces with tunable metaparticles, such as the graphene, liquid crystal, vanadium dioxide, water droplet, microelectromechanical system (MEMS), liquid metal, light‐emitting diodes, PIN diodes, and varactor diodes. [ 47–60 ] However, these existing multifunctional metasurfaces are all metasurfaces for regulating the EM waves. To the best of our knowledge, it has not been reported on the design of multifunctional metasurfaces with thin layer for controlling the radiation, polarization conversion, scattering, and beam scanning.…”

High-precision digital terahertz phase manipulation within a multichannel field perturbation coding 2DEG meta-chip

“…Recently, an information metamaterial [34][35][36][37][38][39][40][41] , as a special digital metamaterial, consisting of coding metaatoms digitalized as "0" or "1" was introduced. The binary codes produce different effects on electromagnetic waves by varying the electromagnetic characteristics of the meta-atoms.…”

Tunable, reconfigurable, and programmable metamaterials

“…The programmable metamaterials are composed of particles in which the pin‐diodes are loaded. By controlling the bias voltages, these diodes show distinct circuit parameters at “ON” and “OFF,” corresponding to the digital codes “0” and “1.” The programmable metamaterials essentially work as the wave‐based information system with programmable coding sequences . When the bias voltages are connected to a field‐programmable gate array (FPGA), the wave based information process on physical levels of metamaterials can be realized in real time.…”

“…The programmable metamaterials essentially work as the wave-based information system with programmable coding sequences. [89][90][91][92][93][94] When the bias voltages are connected to a field-programmable gate array (FPGA), the wave based information process on physical levels of metamaterials can be realized in real time. Different functions can be acquired with the different coding patterns determined by FPGA on programmable metamaterials.…”

“…Different functions can be acquired with the different coding patterns determined by FPGA on programmable metamaterials. In recent years, many functions and devices based on programmable metamaterials have been reported including holograms, 95 imager systems, 89,[96][97][98][99] and communication systems. 90,[100][101][102][103] In this article, we will summarize the recent progress on metamaterials from two aspects: tunable and reconfigurable metamaterials in terahertz and microwave frequencies; the functional devices and novel systems by the programmable metamaterials.…”