Mechanism And Experimental Investigation Of Novel Origami Metasurfaces

For a long time,manipulating electromagnetic waves in designed manners has been an important research goal in the field of electromagnetism.The emerging artificial electromagnetic materials provide a vital platform for free control of electromagnetic waves.As kind of artificial two-dimensional surfaces,metasurfaces are composed of periodical predesigned subwavelength resonators and provide a large degree of control over the flow of electromagnetic waves.To further enhance the versatility of metasurfaces and achieve dynamic control of electromagnetic waves,substantial efforts have been devoted to equip metasurfaces with various tuning mechanisms,facilitating the emergency of the so-called ‘reconfigurable metasurfaces’.However,reconfigurable metasurfaces still face many unsolved problems,for example,achieving continuous wavefront control,realizing dynamic control of electromagnetic waves with ultrawide tuning range and so on.To solve these problems,it is on demand to further explore new mechanisms and design methodologies of artificial metasurfaces for manipulating electromagnetic waves.Origami/kirigami techniques,featuring deformable complex three-dimensional structures via pre-designing folding and/or cutting pattern on a flat sheet of paper.This thesis fully takes advantage of the unique mechanical properties of origami,i.e.,continuous shape transformation and high dimensional deformation.We focus on the issues of previous reconfigurable metasurfaces,systematically investigate origami-based metasurfaces for dynamic control of electromagnetic waves.Continuous wavefront control,topologically reconfigurable magnetic polaritons,multifunctional origami metasurfaces have been realized.Considering the prominent mechanical properties and strong deformation abilities of origami structures,the findings may open an alternative avenue toward lightweight and deployable metadevices with diversified and continuously alterable electromagnetic properties.The content and novelty can be cataloged as follows:1.Aiming at the problem that it is difficult to continuously and dynamically control the wavefront of the electromagnetic waves,we conduct research on origami-based metasurfaces for dynamic control of wavefront.Here,metasurfaces based retroreflector is theoretically proposed for high-efficient spin-locked retroreflection.Upon reflection,the handedness of the waves is kept the same as the incidence.Furthermore,by mechanically altering the folding state of the reconfigurable retroreflector,adaptive tangential momenta could be imparted to the incidence photons,providing a high-performance retroreflection over a continuous range of incidence angles from 27.3° to 52.5°.Moreover,a terahertz spin-locked retroreflector and an ultrathin compact retroreflector have been proposed,with potential applications in not only interface electromagnetics but also ultra-flat photonics.2.Aiming at the problem that it is difficult to regulate energy and momentum of electromagnetic wave simultaneously via metasurfaces,we conduct research on origami-based metasurfaces for dynamic control of energy and momentum of electromagnetic waves.Here,a mechanically tunable origami metasurface capable of either absorbing light energy or modulating light momentum,by incorporating the magnetic meta-atoms into an origami grating,is theoretically designed,and experimentally realized.Through mechanical stretching or compressing of the Miura-ori pattern,the function of origami metasurface can transit from an absorber,a mirror,to a negative reflector.Particularly,the continuously geometric deformation of the Miura-ori lattice is a promising approach to compensate the angular dispersion in gradient metasurfaces.3.Aiming at the problem that it is difficult to modulate the bianisotropy of metasurfaces,we conduct research on the origami-based metasurfaces for dynamic control of bianisotropy.A reconfigurable bianisotropic metasurface is proposed by arranging meta-atoms in a Miura-ori lattice.The bianisotropic properties of origami metasurface are dynamically controlled via the deformation of the Miura-ori pattern,i.e.,zero bianisotropy at planar state and enhanced bianisotropy at folded state.Based on the proposed bianisotropic origami metasurface,controllable asymmetric radiation of a monopole antenna is also demonstrated and asymmetric performance is determined by the origami geometry.4.Aiming at the problem that it is difficult to dynamically regulate polaritons over a wide range,we conduct research on the origami-inspired topologically reconfigurable magnetic polaritons.For the first time,topologically reconfigurable magnetic polaritons in origami metasurface is experimentally reported.It is demonstrated that how the origami techniques fused with artificial magnetism unveil a versatile pathway to manipulate the magnetic polariton dispersions.The three-dimensional origami transformation allows to reconfigure hyperbolic or elliptic topology of the polariton iso-frequency contours and modulate the group velocity of polariton.With group velocity transitioning from positive to negative directions,this thesis further reports integrated polariton circuitry in which the polariton propagation and phase distribution can be tailored.5.Aiming at the problem that it is difficult to efficiently tune macroscopic performance of metasurfaces with little structural/material variation,we conduct research on how to modulate the global electromagnetic response of metasurfaces via localized loss engineering.Firstly,the concept of controlling asymmetric diffraction of metasurfaces based on localized loss is proposed.The asymmetric diffraction ratio can be effectively regulated by the introduced loss.The underlying mechanism of asymmetric diffraction is revealed,and the extremely asymmetric diffraction phenomenon at exceptional point is experimentally verified.Combined with origami deformations,potential applications of localized loss engineering in reconfigurable metasurfaces are prospected.