Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,la...Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,large field of view,and compact device volume.In contrast to conventional holographic displays using bulky conventional diffractive optical elements,metasurface holography enables arbitrary complex wavefront shaping with a much smaller footprint.In this review,we classify metasurface holography according to the meta-atom design methodologies,which can further expand hologram functionalities.We describe light-matter interactions,particularly in metasurface systems,using the relevant the Jones matrix to rigorously explain modulations of the amplitude,phase,and polarization of light.Six different types of metaatoms are presented,and the corresponding achievable wavefronts that form the holographic images in the far-field are also provided.Such a simple classification will give a straightforward approach to design and further realize advanced metasurface holographic devices.展开更多
Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Som...Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Some thermal detectors can achieve realtime imaging by using a focal plane array but have the drawbacks of low sensitivity due to a lack of suitable absorbing materials.In this study,we propose a novel photomechanical meta-molecule array by conveniently assembling THz meta-atom absorbers and bi-material cantilevers together,which can couple THz radiation to a mechanical deflection of the meta-molecules with high efficiency.By optically reading out the mechanical deflections of all of the meta-molecules simultaneously,real-time THz imaging can be achieved.A polyimide sacrificial layer technique was developed to fabricate the device on a glass wafer,which facilitates the transmission of a readout light while the THz wave radiates onto the meta-molecule array directly from the front side.THz images and video of various objects as well as infrared images of the human body were captured successfully with the fabricated metamolecule array.The proposed photomechanical device holds promise in applications in single and broadband THz as well as infrared imaging.展开更多
The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductanc...The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductance incrementally were modeled, simulated, fabricated, and tested to investigate the role inductance plays in metamaterial designs. The designs consisted of strategically adding sections to the SRR to increase the inductance, but in a manner that minimized capacitance variations. Each design showed a shift in resonant frequency that was proportional to the length of the added section. As the length of each section was increased, the resonant frequency shifted from 2.78 GHz to 2.18 GHz.展开更多
基金Hyundai Motor Group,Grant/Award Number:Hyundai Motor Chung Mong-Koo fellowshipLG Display,Grant/Award Number:LGD-SNU incubation programNational Research Foundation of Korea,Grant/Award Numbers:CAMM-2019M3A6B3030637,NRF-2019R1A2C3003129,NRF-2019R1A5A8080290,NRF-2021R1C1C2004291。
文摘Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,large field of view,and compact device volume.In contrast to conventional holographic displays using bulky conventional diffractive optical elements,metasurface holography enables arbitrary complex wavefront shaping with a much smaller footprint.In this review,we classify metasurface holography according to the meta-atom design methodologies,which can further expand hologram functionalities.We describe light-matter interactions,particularly in metasurface systems,using the relevant the Jones matrix to rigorously explain modulations of the amplitude,phase,and polarization of light.Six different types of metaatoms are presented,and the corresponding achievable wavefronts that form the holographic images in the far-field are also provided.Such a simple classification will give a straightforward approach to design and further realize advanced metasurface holographic devices.
基金This study was funded by the National Natural Science Foundation of China(Grants No.61575003)the China Postdoctoral Science Foundation(Grants Nos.2015M580096 and 2017T100074).
文摘Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Some thermal detectors can achieve realtime imaging by using a focal plane array but have the drawbacks of low sensitivity due to a lack of suitable absorbing materials.In this study,we propose a novel photomechanical meta-molecule array by conveniently assembling THz meta-atom absorbers and bi-material cantilevers together,which can couple THz radiation to a mechanical deflection of the meta-molecules with high efficiency.By optically reading out the mechanical deflections of all of the meta-molecules simultaneously,real-time THz imaging can be achieved.A polyimide sacrificial layer technique was developed to fabricate the device on a glass wafer,which facilitates the transmission of a readout light while the THz wave radiates onto the meta-molecule array directly from the front side.THz images and video of various objects as well as infrared images of the human body were captured successfully with the fabricated metamolecule array.The proposed photomechanical device holds promise in applications in single and broadband THz as well as infrared imaging.
文摘The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductance incrementally were modeled, simulated, fabricated, and tested to investigate the role inductance plays in metamaterial designs. The designs consisted of strategically adding sections to the SRR to increase the inductance, but in a manner that minimized capacitance variations. Each design showed a shift in resonant frequency that was proportional to the length of the added section. As the length of each section was increased, the resonant frequency shifted from 2.78 GHz to 2.18 GHz.
