Electromagnetic Real-time Manipulation And The Applications Of Programmable Metasurfaces

Metasurfaces are ultrathin array structures that consist of subwavelength artificial elements distributed on a two-dimensional surface in accordance with the specific arrangement rules,which have strong electromagnetic(EM)control capabilities.Metasurface can not only manipulate precisely the physical characteristics of EM waves in subwavelength scale,but also has many advantages(such as thin thickness,easily conformal and relatively simple fabrication)for engineering application,and has aroused enormous interest and extensive attention in many fields.In 2014,digital coding and programmable metasurfaces proposed by Prof.Tie Jun Cui et al.from Southeast University brought new vitality into the research of metasurfaces,enabling us to design metasurfaces from the perspective of digital information.The flexible control of EM fields and waves can be achieved by changing the coding sequences of digital coding and programmable metasurfaces,which simplifies the procedure for EM-manipulation using metasurfaces.Importantly,it connects the metasurface physical space with a digital space,allowing control the EM physical properties and process digital information simultaneously on one platform.Programmable metasurface is capable of generating various functions in real time through digital programming manner,and thus hold extraordinary potentials to construct multifunctional EM devices and new architecture of electronic information systems.In this thesis,we focus on the systematic investigation of programmable metasurfaces from the perspectives of control method,manipulation feature,functionalities,performance,and applications,showing their powerful real-time EM control ability and important applications by theoretical analysis,structural design,numerical simulation and experimental test.The main contents and contributions of this thesis are summarized as follows:1)An optical control scheme for controlling EM metasurfaces remotely is proposed.Based on this method,the light-controllable reflective digital coding metasurface and the light-controllable transmissive digital coding metasurface are designed and realized.The concept of using digital coding method to quantify amplitude of EM waves is also proposed.The experimental results show that under external different illumination intensities,the two fabricated optically controlled digital coding metasurfaces can be used to tailor dynamically the reflection beam and transmission amplitude of EM waves,respectively.The proposed optical control scheme can simplify effectively the feed network design and enrich the control mode of dynamic metasurfaces,which is helpful for the design of multi-physics metasurfaces and non-contact remote control metasurfaces.2)A highly-integrated broadband optically driven programmable metasurface is proposed and implemented by integrating multiple independent optical interrogation networks on the back of the designed dynamic metasurface.Such the metasurface can tune the distribution of microwave reflection phase wirelessly by receiving different light patterns,and then generate different EM functions in real time.As examples,the metasurface sample is controlled by different illumination patterns in the experiment for achieving external cloaking,EM illusion and dynamic vortex beam generation,and the measured results are in good agreement with the simulation ones,which verifies that the EM physical characteristics can be controlled by light on a single metasurface platform,thus providing an interface for connecting optical signal and microwave signal.3)The low-profile passive digital coding array antenna and the low-profile pattern reconfigurable programmable array antenna without space-feed structure are proposed and designed.The simulation and experimental verifications are carried out,and all the results indicate that the digital coding method can be adopted to control EM radiation waves directly.4)A dual-polarization independently programmable metasurface that can achieve decoupling control of orthogonally-polarized waves is proposed and constructed.Such the metasurface can provide two independent EM channels,expanding the capability and function of the programmable metasurfaces.As examples,a wave-based exclusive-OR logic operation platform for spin control of circularly-polarized waves,a fixed-frequency wide-angle dual-beam scanning antenna and a dual-polarized shared-aperture antenna are demonstrated using the single metasurface,which are all well verified in the simulations and experiments.5)A time-modulated programmable metasurface with wideband and full polarization features is proposed and designed,and its principle of generating high efficiency frequency conversion is also analyzed.Based on this time-modulated programmable metasurface and the designed adaptive control circuit,a smart Doppler cloaking system is developed,which can hide Doppler shift self-adaptively according to the velocity of moving objects.The experimental results show that the smart Doppler cloaking system has excellent performance under incidences of EM waves with different polarizations and different frequencies,which verifies the feasibility of achieveing intelligent manipulation of EM waves in time domain.6)An optically programmed time-modulated metasurface for direct conversion from visible signal to microwave signal is proposed and designed.Based on the optically programmed time-modulated metasurface,a hybrid communication system prototype is constructed.Such the metasurface platform can map the information carried by the light signal to the microwave carrier directly,without complex relay.In the experiments,the communication performance of the hybrid communication system is verified by transmitting pictures.The results show that the hybrid communication system is able to transmit and receive information through the visible light link and the microwave link respectively,achieving the real-time transmission of data.