Complex-amplitude holographic metasurfaces(CAHMs)with the flexibility in modulating phase and amplitude profiles have been used to manipulate the propagation of wavefront with an unprecedented level,leading to higher ...Complex-amplitude holographic metasurfaces(CAHMs)with the flexibility in modulating phase and amplitude profiles have been used to manipulate the propagation of wavefront with an unprecedented level,leading to higher image-reconstruction quality compared with their natural counterparts.However,prevailing design methods of CAHMs are based on Huygens-Fresnel theory,meta-atom optimization,numerical simulation and experimental verification,which results in a consumption of computing resources.Here,we applied residual encoder-decoder convolutional neural network to directly map the electric field distributions and input images for monolithic metasurface design.A pretrained network is firstly trained by the electric field distributions calculated by diffraction theory,which is subsequently migrated as transfer learning framework to map the simulated electric field distributions and input images.The training results show that the normalized mean pixel error is about 3%on dataset.As verification,the metasurface prototypes are fabricated,simulated and measured.The reconstructed electric field of reverse-engineered metasurface exhibits high similarity to the target electric field,which demonstrates the effectiveness of our design.Encouragingly,this work provides a monolithic field-to-pattern design method for CAHMs,which paves a new route for the direct reconstruction of metasurfaces.展开更多
The retroreflector based on a gradient metasurface can reflect electromagnetic(EM)waves to the source,and it is small in size and lightweight.However,even if the previous retroreflectors can be used for angle adaptati...The retroreflector based on a gradient metasurface can reflect electromagnetic(EM)waves to the source,and it is small in size and lightweight.However,even if the previous retroreflectors can be used for angle adaptation,the working efficiency declines sharply at large angles.In this paper,a retroreflector is designed based on a reconfigurable origami two-dimensional(2D)metagrating for efficient spin-locked retroreflection and for suppressing unwanted Floquet diffraction channels.After the retroreflection,the handedness of the wave remains consistent with the incident.By changing the folding state of the origami metagrating,the adaptive tangential momentum can be transferred to the incident wave,providing high-performance retroreflection over a continuous incidence angle range of 30°–45.8°(x-direction)and 30°–81°(y-direction).As proof of concept,an electric metagrating-based retroreflector is fabricated in the microwave frequency band,and the simulation and experimental results are consistent.This adaptive origami spin-locked metasurface has promising applications in spin-optics devices,communication systems,remote sensing,and radar cross-section(RCS)enhancement.展开更多
To the Editor:For patients with critical tracheal stenosis in surgery,extracorporeal membrane oxygenation(ECMO)is probably the last,yet safest,choice to ensure definitive airway security.Systemic anticoagulation in th...To the Editor:For patients with critical tracheal stenosis in surgery,extracorporeal membrane oxygenation(ECMO)is probably the last,yet safest,choice to ensure definitive airway security.Systemic anticoagulation in the form of heparin is a typical choice.However,heparin is fraught with its own complications that include both bleeding in the patient and clotting within the circuitry.展开更多
Polarization is one of the basic characteristics of electromagnetic(EM)waves,and its flexible control is very important in many practical applications.At present,most of the multifunction polarization metasurfaces are...Polarization is one of the basic characteristics of electromagnetic(EM)waves,and its flexible control is very important in many practical applications.At present,most of the multifunction polarization metasurfaces are electrically tunable based on PIN and varactor diodes,which are easy to operate and have strong real-time performance.However,there are still some problems in them,such as few degrees of freedom of planar structure control,complex circuit,bulky sample,and high cost.In view of these shortcomings,this paper proposes a Miura origami based reconfigurable polarization conversion metasurface for multifunctional control of EM waves.The interaction between the electric dipoles is changed by adjusting the folding angleθ,thereby tuning the operating frequency of the polarization conversion and the polarization state of the reflected wave.This mechanical control method brings more degrees of freedom to manipulate EM waves.And the processed sample is with lightweight and low cost.To verify the performance of the proposed origami polarization converter,a Miura origami structure loaded with metal split rings is designed and fabricated.The operating frequency of the structure can be tuned in different folding states.In addition,by controlling the folding angleθ,linear-to-linear and linear-to-circular polarization converters can be realized at different folding states.The proposed Miura origami polarization conversion metasurface provides a new idea for reconfigurable linear polarization conversion and multifunctional devices.展开更多
Coding metasurfaces can manipulate electromagnetic wave in real time with high degree of freedom,the fascinating properties of which enrich the metasurface design with a wide range of application prospects.However,mos...Coding metasurfaces can manipulate electromagnetic wave in real time with high degree of freedom,the fascinating properties of which enrich the metasurface design with a wide range of application prospects.However,most of the coding metasurfaces are designed based on external excitation framework with the wired electrical or wireless light control devices,thus inevitably causing the interference with electromagnetic wave transmission and increasing the complexity of the metasurface design.In this work,a simplistic framework of single-pixel-programmable metasurfaces integrated with a capsuled LED array is proposed to dynamically control electromagnetic wave.The framework fully embeds the photoresistor in the meta-atom,controlling the LED array to directly illuminate the photoresistor to modulate the phase response.With this manner,the complex biasing network is transformed to the universal LED array,which means the physical control framework can be transformed to a software framework,and thus the functions of the metasurface can be freely manipulated by encoding the capsuled LED array avoiding mutual coupling of adjacent meta-atoms in real time.All the results verify that the far-field scattering pattern can be customized with this singlepixel-programmable metasurface.Encouragingly,this work provides a universal framework for coding metasurface design,which lays the foundation for metasurface intelligent perception and adaptive modulation.展开更多
Chiral mirrors can produce spin selective absorption for left-handed circularly polarized(LCP) or right-handed circularly polarized(RCP) waves. However, the previously proposed chiral mirror only absorbs the designate...Chiral mirrors can produce spin selective absorption for left-handed circularly polarized(LCP) or right-handed circularly polarized(RCP) waves. However, the previously proposed chiral mirror only absorbs the designated circularly polarized(CP) wave in the microwave frequency band, lacking versatility in practical applications.Here, we propose a switchable chiral mirror based on a pair of PIN diodes. The switchable chiral mirror has four working states, switching from the handedness-preserving mirror to the LCP mirror, RCP mirror, and perfect absorber. The basis of these advances is to change the chirality of two-dimensional(2D) chiral metamaterials and the circular conversion dichroism related to it, which is the first report in the microwave frequency band.Surface current distributions shed light on how switchable chiral mirrors work by handedness-selective excitation of reflective and absorbing electric dipole modes. Energy loss distributions verify the working mechanism. The thickness of the switchable chiral mirror is one-tenth of the working wavelength, which is suitable for integrated manufacturing. The measurement results are in good agreement with the simulation results.展开更多
基金supports from the National Natural Science Foundation of China under Grant Nos.61971435,62101588,62101589Natural Science Basic Research Program of Shaanxi Province(Grant No:2022JM-352,2022JQ-335,2023-JC-YB-069)the National Key Research and Development Program of China(Grant No.:SQ2017YFA0700201).
文摘Complex-amplitude holographic metasurfaces(CAHMs)with the flexibility in modulating phase and amplitude profiles have been used to manipulate the propagation of wavefront with an unprecedented level,leading to higher image-reconstruction quality compared with their natural counterparts.However,prevailing design methods of CAHMs are based on Huygens-Fresnel theory,meta-atom optimization,numerical simulation and experimental verification,which results in a consumption of computing resources.Here,we applied residual encoder-decoder convolutional neural network to directly map the electric field distributions and input images for monolithic metasurface design.A pretrained network is firstly trained by the electric field distributions calculated by diffraction theory,which is subsequently migrated as transfer learning framework to map the simulated electric field distributions and input images.The training results show that the normalized mean pixel error is about 3%on dataset.As verification,the metasurface prototypes are fabricated,simulated and measured.The reconstructed electric field of reverse-engineered metasurface exhibits high similarity to the target electric field,which demonstrates the effectiveness of our design.Encouragingly,this work provides a monolithic field-to-pattern design method for CAHMs,which paves a new route for the direct reconstruction of metasurfaces.
基金supported by the National Natural Science Foundation of China(Nos.61971437,61971341,and 61971435)the National Key Research and Development Program of China(No.2022YFB3806200)。
文摘The retroreflector based on a gradient metasurface can reflect electromagnetic(EM)waves to the source,and it is small in size and lightweight.However,even if the previous retroreflectors can be used for angle adaptation,the working efficiency declines sharply at large angles.In this paper,a retroreflector is designed based on a reconfigurable origami two-dimensional(2D)metagrating for efficient spin-locked retroreflection and for suppressing unwanted Floquet diffraction channels.After the retroreflection,the handedness of the wave remains consistent with the incident.By changing the folding state of the origami metagrating,the adaptive tangential momentum can be transferred to the incident wave,providing high-performance retroreflection over a continuous incidence angle range of 30°–45.8°(x-direction)and 30°–81°(y-direction).As proof of concept,an electric metagrating-based retroreflector is fabricated in the microwave frequency band,and the simulation and experimental results are consistent.This adaptive origami spin-locked metasurface has promising applications in spin-optics devices,communication systems,remote sensing,and radar cross-section(RCS)enhancement.
基金Beijing Hospitals Authority Clinical Medicine Development of Special Funding Support(No.ZYLX202103)Beijing Hospitals Authority’s Ascent Plan(No.DFL20220203)
文摘To the Editor:For patients with critical tracheal stenosis in surgery,extracorporeal membrane oxygenation(ECMO)is probably the last,yet safest,choice to ensure definitive airway security.Systemic anticoagulation in the form of heparin is a typical choice.However,heparin is fraught with its own complications that include both bleeding in the patient and clotting within the circuitry.
基金National Key Research and Development Program of China(2022YFB3806200)National Natural Science Foundation of China(61971341,61971435,61971437)。
文摘Polarization is one of the basic characteristics of electromagnetic(EM)waves,and its flexible control is very important in many practical applications.At present,most of the multifunction polarization metasurfaces are electrically tunable based on PIN and varactor diodes,which are easy to operate and have strong real-time performance.However,there are still some problems in them,such as few degrees of freedom of planar structure control,complex circuit,bulky sample,and high cost.In view of these shortcomings,this paper proposes a Miura origami based reconfigurable polarization conversion metasurface for multifunctional control of EM waves.The interaction between the electric dipoles is changed by adjusting the folding angleθ,thereby tuning the operating frequency of the polarization conversion and the polarization state of the reflected wave.This mechanical control method brings more degrees of freedom to manipulate EM waves.And the processed sample is with lightweight and low cost.To verify the performance of the proposed origami polarization converter,a Miura origami structure loaded with metal split rings is designed and fabricated.The operating frequency of the structure can be tuned in different folding states.In addition,by controlling the folding angleθ,linear-to-linear and linear-to-circular polarization converters can be realized at different folding states.The proposed Miura origami polarization conversion metasurface provides a new idea for reconfigurable linear polarization conversion and multifunctional devices.
基金National Key Research and Development Program of China(2022YFB3806200)National Natural Science Foundation of China(12004437,61971435,62101588,62201609,62001504)Natural Science Foundation of Shaanxi Province(2022JM-352,2022JQ-630)。
文摘Coding metasurfaces can manipulate electromagnetic wave in real time with high degree of freedom,the fascinating properties of which enrich the metasurface design with a wide range of application prospects.However,most of the coding metasurfaces are designed based on external excitation framework with the wired electrical or wireless light control devices,thus inevitably causing the interference with electromagnetic wave transmission and increasing the complexity of the metasurface design.In this work,a simplistic framework of single-pixel-programmable metasurfaces integrated with a capsuled LED array is proposed to dynamically control electromagnetic wave.The framework fully embeds the photoresistor in the meta-atom,controlling the LED array to directly illuminate the photoresistor to modulate the phase response.With this manner,the complex biasing network is transformed to the universal LED array,which means the physical control framework can be transformed to a software framework,and thus the functions of the metasurface can be freely manipulated by encoding the capsuled LED array avoiding mutual coupling of adjacent meta-atoms in real time.All the results verify that the far-field scattering pattern can be customized with this singlepixel-programmable metasurface.Encouragingly,this work provides a universal framework for coding metasurface design,which lays the foundation for metasurface intelligent perception and adaptive modulation.
基金National Natural Science Foundation of China (61971341, 61971435, 61971437)Natural Science Foundation of Shaanxi Province (2020JM-342, 2022JQ-630)。
文摘Chiral mirrors can produce spin selective absorption for left-handed circularly polarized(LCP) or right-handed circularly polarized(RCP) waves. However, the previously proposed chiral mirror only absorbs the designated circularly polarized(CP) wave in the microwave frequency band, lacking versatility in practical applications.Here, we propose a switchable chiral mirror based on a pair of PIN diodes. The switchable chiral mirror has four working states, switching from the handedness-preserving mirror to the LCP mirror, RCP mirror, and perfect absorber. The basis of these advances is to change the chirality of two-dimensional(2D) chiral metamaterials and the circular conversion dichroism related to it, which is the first report in the microwave frequency band.Surface current distributions shed light on how switchable chiral mirrors work by handedness-selective excitation of reflective and absorbing electric dipole modes. Energy loss distributions verify the working mechanism. The thickness of the switchable chiral mirror is one-tenth of the working wavelength, which is suitable for integrated manufacturing. The measurement results are in good agreement with the simulation results.
