Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics ...Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics of plasmonic vortices,providing a better understanding of optical orbital angular momentums in the evanescent wave regime.However,these works only focused on the objective characterization of plasmonic vortex and have not achieved subjectively tailoring of its spatiotemporal dynamics for specific applications.Herein,it is demonstrated that the plasmonic vortices with the same topological charge can be endowed with distinct spatiotemporal dynamics by simply changing the coupler design.Based on a near-field scanning terahertz microscopy,the surface plasmon fields are directly obtained with ultrahigh spatiotemporal resolution,experimentally exhibiting the generation and evolution divergences during the whole lifetime of plasmonic vortices.The proposed strategy is straightforward and universal,which can be readily applied into visible or infrared frequencies,facilitating the development of plasmonic vortex related researches and applications.展开更多
Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are...Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at theГpoint of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C_(2)T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at the r point of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C2T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.展开更多
Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, a...Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices.展开更多
By allowing almost arbitrary distributions of amplitude and phase of electromagnetic waves to be generated by a layer of sub-wavelength-size unit cells,metasurfaces have given rise to the field of meta-holography.Howe...By allowing almost arbitrary distributions of amplitude and phase of electromagnetic waves to be generated by a layer of sub-wavelength-size unit cells,metasurfaces have given rise to the field of meta-holography.However,holography with circularly polarized waves remains complicated as the achiral building blocks of existing meta-holograms inevitably contribute to holographic images generated by both left-handed and right-handed waves.Here we demonstrate how planar chirality enables the fully independent realization of high-efficiency meta-holograms for one circular polarization or the other.Such circular-polarization-selective meta-holograms are based on chiral building blocks that reflect either left-handed or right-handed circularly polarized waves with an orientation-dependent phase.Using terahertz waves,we experimentally demonstrate that this allows the straightforward design of reflective phase meta-holograms,where the use of alternating structures of opposite handedness yields independent holographic images for circularly polarized waves of opposite handedness with negligible polarization cross-talk.展开更多
Terahertz science and technology promise many cutting-edge applications.Terahertz surface plasmonic waves that propagate at metal–dielectric interfaces deliver a potentially effective way to realize integrated terahe...Terahertz science and technology promise many cutting-edge applications.Terahertz surface plasmonic waves that propagate at metal–dielectric interfaces deliver a potentially effective way to realize integrated terahertz devices and systems.Previous concerns regarding terahertz surface plasmonic waves have been based on their highly delocalized feature.However,recent advances in plasmonics indicate that the confinement of terahertz surface plasmonic waves,as well as their propagating behaviors,can be engineered by designing the surface environments,shapes,structures,materials,etc.,enabling a unique and fascinating regime of plasmonic waves.Together with the essential spectral property of terahertz radiation,as well as the increasingly developed materials,microfabrication,and time-domain spectroscopy technologies,devices and systems based on terahertz surface plasmonic waves may pave the way toward highly integrated platforms for multifunctional operation,implementation,and processing of terahertz waves in both fundamental science and practical applications.We present a review on terahertz surface plasmonic waves on various types of supports in a sequence of properties,excitation and detection,and applications.The current research trend and outlook of possible research directions for terahertz surface plasmonic waves are also outlined.展开更多
Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational...Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational circular dichroism.In the THz regime,the lack of a polarization modulator hinders the development of this spectroscopy.We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials(CMMs)integrated with Ge_(2)Sb_(2)Te_(5)(GST225)active components can achieve nonvolatile and continuously tunable optical activity in the THz region.A THz time-domain spectroscopic system was used to characterize the device,showing a tunable ellipticity(from‒36°to 0°)and rotation of the plane polarization(from 32°to 0°)at approximately 0.73 THz by varying the GST225 state from amorphous(AM)to crystalline(CR).Moreover,a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225,which can create intermediate states,having regions of both AM and CR states.Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state.Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.展开更多
Superconducting terahertz metamaterials have attracted significant interest due to low loss, efficient resonance switching and large-range frequency tunability. The super conductivity in the metamaterials dramatically...Superconducting terahertz metamaterials have attracted significant interest due to low loss, efficient resonance switching and large-range frequency tunability. The super conductivity in the metamaterials dramatically reduces ohmic loss and absorption to levels suitable for novel devices over a broad range of electromagnetic spectrum. Most metamaterials utilize subwavelength-scale split-ring resonators as unit building blocks, which are proved to support fundamental inductive-capacitive reso- nance, to achieve unique resonance performance. We presented a review of terahertz superconducting metama- terials and their implementation in multifunctional devices. We began with the recent development of superconducting metamaterials and their potential applications in control- ling and manipulating terahertz waves. Then we explored the tuning behaviors of resonance properties in several typical, actively controllable metamaterials through integrating active components. Finally, the ultrafast dynamic nonlinear response to high intensity terahertz field in the superconducting metamaterials was presented.展开更多
基金supported by the National Natural Science Foundation of China(62005193,62135008,62075158,62025504,61935015)the National Science Foundation(2114103)Guangxi Key Laboratory of Optoelectroric Information Processing(GD20202).
文摘Plasmonic vortices confining orbital angular momentums to surface have aroused wide research interest in the last decade.Recent advances of near-field microscopes have enabled the study on the spatiotemporal dynamics of plasmonic vortices,providing a better understanding of optical orbital angular momentums in the evanescent wave regime.However,these works only focused on the objective characterization of plasmonic vortex and have not achieved subjectively tailoring of its spatiotemporal dynamics for specific applications.Herein,it is demonstrated that the plasmonic vortices with the same topological charge can be endowed with distinct spatiotemporal dynamics by simply changing the coupler design.Based on a near-field scanning terahertz microscopy,the surface plasmon fields are directly obtained with ultrahigh spatiotemporal resolution,experimentally exhibiting the generation and evolution divergences during the whole lifetime of plasmonic vortices.The proposed strategy is straightforward and universal,which can be readily applied into visible or infrared frequencies,facilitating the development of plasmonic vortex related researches and applications.
基金This work is supported by the Research Grants Council of Hong Kong,China(AoE/P-02/12,16304717,16310420)the Hong Kong Scholars Program(XJ2019007)+2 种基金W.-J.C.is supported by the National Natural Science Foundation of China(Grant no.11874435)J.H.is supported by the National Natural Science Foundation of China(Grant no.62025504,61935015)S.Z.acknowledges support from the ERC Consolidator Grant(TOPOLOGICAL),the Royal Society,and the Wolfson Foundation.
文摘Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at theГpoint of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C_(2)T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at the r point of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C2T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.
基金National Basic Research Program of China(2014CB339800)National Natural Science Foundation of China(NSFC)(61420106006,61422509,61605143,61622505,61675145,61735012)+2 种基金Program for Changjiang Scholars and Innovative Research Team in University(IRT13033)Major National Development Project of Scientific Instruments and Equipment(2011YQ150021)Guangxi Key Laboratory of Automatic Detecting Technology and Instruments(YQ17203)
文摘Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices.
基金supported by the National Natural Science Foundation of China(grant nos.61422509,61307125,61427814,61420106006,and 61328503)the National Key Basic Research Special Foundation of China(grant no.2014CB339800)+2 种基金the Program for Changjiang Scholars and Innovative Research Team in Universities(grant no.IRT13033)the UK’s Engineering and Physical Sciences Research Council(grant no.EP/M009122/1)the US National Science Foundation(grant no.ECCS-1232081)。
文摘By allowing almost arbitrary distributions of amplitude and phase of electromagnetic waves to be generated by a layer of sub-wavelength-size unit cells,metasurfaces have given rise to the field of meta-holography.However,holography with circularly polarized waves remains complicated as the achiral building blocks of existing meta-holograms inevitably contribute to holographic images generated by both left-handed and right-handed waves.Here we demonstrate how planar chirality enables the fully independent realization of high-efficiency meta-holograms for one circular polarization or the other.Such circular-polarization-selective meta-holograms are based on chiral building blocks that reflect either left-handed or right-handed circularly polarized waves with an orientation-dependent phase.Using terahertz waves,we experimentally demonstrate that this allows the straightforward design of reflective phase meta-holograms,where the use of alternating structures of opposite handedness yields independent holographic images for circularly polarized waves of opposite handedness with negligible polarization cross-talk.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.61935015,61735012,61605143,61622505,61575141,61722509,61675145,and 61775159)the Tianjin Municipal Fund for Distinguished Young Scholars(Grant No.18JCJQJC45600).
文摘Terahertz science and technology promise many cutting-edge applications.Terahertz surface plasmonic waves that propagate at metal–dielectric interfaces deliver a potentially effective way to realize integrated terahertz devices and systems.Previous concerns regarding terahertz surface plasmonic waves have been based on their highly delocalized feature.However,recent advances in plasmonics indicate that the confinement of terahertz surface plasmonic waves,as well as their propagating behaviors,can be engineered by designing the surface environments,shapes,structures,materials,etc.,enabling a unique and fascinating regime of plasmonic waves.Together with the essential spectral property of terahertz radiation,as well as the increasingly developed materials,microfabrication,and time-domain spectroscopy technologies,devices and systems based on terahertz surface plasmonic waves may pave the way toward highly integrated platforms for multifunctional operation,implementation,and processing of terahertz waves in both fundamental science and practical applications.We present a review on terahertz surface plasmonic waves on various types of supports in a sequence of properties,excitation and detection,and applications.The current research trend and outlook of possible research directions for terahertz surface plasmonic waves are also outlined.
基金the National Key Research and Development Program of China(2019YFA0709100,2020YFA0714504)the LiaoNing Revitalization Talents Program(Grant No.XLYC1807237).
文摘Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational circular dichroism.In the THz regime,the lack of a polarization modulator hinders the development of this spectroscopy.We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials(CMMs)integrated with Ge_(2)Sb_(2)Te_(5)(GST225)active components can achieve nonvolatile and continuously tunable optical activity in the THz region.A THz time-domain spectroscopic system was used to characterize the device,showing a tunable ellipticity(from‒36°to 0°)and rotation of the plane polarization(from 32°to 0°)at approximately 0.73 THz by varying the GST225 state from amorphous(AM)to crystalline(CR).Moreover,a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225,which can create intermediate states,having regions of both AM and CR states.Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state.Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.
文摘Superconducting terahertz metamaterials have attracted significant interest due to low loss, efficient resonance switching and large-range frequency tunability. The super conductivity in the metamaterials dramatically reduces ohmic loss and absorption to levels suitable for novel devices over a broad range of electromagnetic spectrum. Most metamaterials utilize subwavelength-scale split-ring resonators as unit building blocks, which are proved to support fundamental inductive-capacitive reso- nance, to achieve unique resonance performance. We presented a review of terahertz superconducting metama- terials and their implementation in multifunctional devices. We began with the recent development of superconducting metamaterials and their potential applications in control- ling and manipulating terahertz waves. Then we explored the tuning behaviors of resonance properties in several typical, actively controllable metamaterials through integrating active components. Finally, the ultrafast dynamic nonlinear response to high intensity terahertz field in the superconducting metamaterials was presented.