[Southeast University News Network, April 18] (Correspondent: Zhang Xin’ge) Recently, Academician Cui Tiejun’s research team from Southeast University, in cooperation with Professor Qiu Chengwei from the National University of Singapore, proposed, designed and experimentally verified the dual-channel independently programmable metasurfaces with strong reconfiguration capability. The dual-programmable metasurfaces highlightan independent control interface, which can independently program, regulate andcontrol the x-polarized and y-polarized electromagnetic waves in real time, thereby realizing multiple complex and novel electromagnetic functions. Compared with previous single-polarized programmable metasurfaces, the dual-programmable metasurfaces can provide two mutually independent information transmission channels in parallel, which have greatly improved the information processing capability of such programmable metasurfaces.

Related research results were published in the comprehensive academic journal “Advanced Science” under the title of “Polarization-controlled dual-programmable metasurfaces”. The corresponding authors include Prof. Jiang Weixiang and Prof. Cui Tiejun from Southeast University and Prof. Qiu Chengwei from the National University of Singapore. The first author is Zhang Xin’ge, a doctoral student of Southeast University.

Polarization-controlled dual programmable metasurfaces and the functional schematic diagram

The metasurface, as an ultra-thin platform composed of sub-wavelength artificial units arranged on a two-dimensional surface in a periodic or non-periodic manner, exhibits powerful capabilities in regulating electromagnetic waves. In particular, the dynamic metasurfaces can artificially and dynamically control electromagnetic waves under external control signals. At present, the majority dynamic metasurfaces are adjustable and reconfigurable. Their functions can be slightly adjustable but with great similarity; the reconfigurable metasurfaces can obtain significantly distinctive but limited functions. In order to realize real-time control and switchover among many different functions, Prof. Cui Tiejun et al. proposed introducing the digital coding representation and the field programmable logic gate array (FPGA) into the design of dynamic metasurfaces in 2014. As a result, the field programmable metasurfaces have been realized, highlighting many completely different functions accessible on a single platform andswitchable in real time according to the set programs. However, the majority existing programmable metasurfaces can only be programmable when irradiated by specific polarization electromagnetic waves designed in advance and still maintain static when irradiated by other polarization electromagnetic waves. As the programmable metasurfaces can only be controlled in real time under the irradiation of single polarized electromagnetic waves and can only provide one effective information transmission channel, they can only process multiple tasks in series on one channel, which has limited their capacity of processing multiple tasks in parallel.

In order to improve the information processing efficiency and the multi-task processing capabilities of the metasurfaces, researchers have developed and designed a kind of dual-polarized metasurfaces that can respond to electromagnetism differentially under different polarizations and thus provide two independent information channels in parallel. Compared to the single-polarized metasurfaces, the dual-polarized metasurfaces can achieve muchmore complex functions, such as multi-channel information processing, polarization division multiplexing and dual-polarized caliber sharing. Inthis sense, the dual-polarized metasurfaces can realize more advanced functional devices. However, the current dual-polarized metasurfaces are static or can only be slightly adjustable, as a result, their functions cannot be switched by real-time programming, which has greatly limited their versatility and application to ultrafast switching and scanning systems.

In order to solve the above problem, the researchers designed a kind of dual-programmable metasurfaces that can independently regulate the x-polarized and y-polarized electromagnetic waves. To this end, the researchers first carefully designed a kind of active metasurface units capable for independently regulating the reflection phase of x-polarized and y-polarized electromagnetic waves. Such active metasurface units feature a specially designed metal pattern and integrate two varactors in the x direction and the y direction respectively. And the capacitance of such two varactors can be independently regulated at these two directions via two bias lines as designed so as to control the reflection phase of the x-polarized and y-polarized electromagnetic waves independently. In order to obtain the dual-programmable metasurfaces and implement multiple complex electromagnetic functions, the researchers adopted 24x24 metasurface units to form an array that contained 48 independent control interfaces. In order to effectively control the dual-programmable metasurfaces containing multiple independent control interfaces via a single FPGA, the researchers further designed and implemented an extended interface circuit and a DC voltage conversion circuit, the former of which, mainly composed of a decoder and a latch, can greatly expand few FPGA interfaces in an exponential manner. Meanwhile, the voltage conversion circuit, mainly composed of transistors and resistors, can convert the voltage output from the FPGA to the bias voltage as demanded by the varactors in the dual-programmable metasurfaces. In this way, the dual-programmable metasurface platform as finally developed features rich programmability and can realize multiple complex electromagnetic functions. As demonstrated in the experiment, the researchers have experimentally verified three different electromagnetic functions on a single platform for XOR logic operations controlled by spinning of circularly polarized waves, fixed-frequency large-angle dual-beam scanning and dual-polarized caliber sharing respectively. Thus such dual-programmable metasurfaces have provided a new technological solution to develop large-scale, highly-integrated electromagnetic devices and systems; in addition, they are expected to be applied to advanced devices and systems such as wave-based logic computing platforms, high-speed scanning radars and multi-channel spatial light processors, etc..

Submitted by: School of Information Science and Engineering

(Editor-in-charge: Wu Hanyu, reviewed by: Song Yechun)