If a metalens integrates the circular polarization(CP)conversion function,the focusing lens together with circular-polariz-ing lens(CPL)in traditional cameras may be replaced by a metalens.However,in terahertz(THz)ban...If a metalens integrates the circular polarization(CP)conversion function,the focusing lens together with circular-polariz-ing lens(CPL)in traditional cameras may be replaced by a metalens.However,in terahertz(THz)band,the reported metalenses still do not obtain the perfect and strict single-handed CP,because they were constructed via Pancharatnam-Berry phase so that CP conversion contained both left-handed CP(LCP)and right-handed CP(RCP)components.In this paper,a silicon based THz metalens is constructed using dynamic phase to obtain single-handed CP conversion.Also,we can rotate the whole metalens at a certain angle to control the conversion of multi-polarization states,which can simply manipulate the focusing for incident linear polarization(LP)THz wave in three polarization conversion states,in-cluding LP without conversion,LCP and RCP.Moreover,the polarization conversion behavior is reversible,that is,the THz metalens can convert not only the LP into arbitrary single-handed CP,but also the LCP and RCP into two perpen-dicular LP,respectively.The metalens is expected to be used in advanced THz camera,as a great candidate for tradi-tional CPL and focusing lens group,and also shows potential application in polarization imaging with discriminating LCP and RCP.展开更多
Metasurfaces that can realize the polarization manipulation of electromagnetic waves on the sub-wavelength scale have become an emerging research field.Here,a novel strategy of combining the metasurface and Fresnel zo...Metasurfaces that can realize the polarization manipulation of electromagnetic waves on the sub-wavelength scale have become an emerging research field.Here,a novel strategy of combining the metasurface and Fresnel zone plate to form a metasurface zone plate is proposed to realize the conversion from nearly arbitrary polarizations to a fixed polarization.Specifically,when one polarized wave is incident on adjacent ring zones constructed by different types of meta-atoms,the transmitted waves generated by odd-numbered and even-numbered ring zones converge at the same focus and superimpose to generate a fixed polarized wave.As function demonstrations,we have designed two types of metasurface zone plates:one is a focused linear polarizer,and the other can convert nearly arbitrary polarized waves into focused circularly polarized waves.The simulated and measured results are consistent with theoretical expectations,suggesting that the proposed concept is flexible and feasible.Our work provides an alternative platform for polarization manipulation and may vigorously promote the development of polarization photonic devices.展开更多
Strong terahertz(THz)radiation provides a powerful tool to manipulate and control complex condensed matter systems.This review provides an overview of progress in the generation,detection,and applications of intense T...Strong terahertz(THz)radiation provides a powerful tool to manipulate and control complex condensed matter systems.This review provides an overview of progress in the generation,detection,and applications of intense THz radiation.The tabletop intense THz sources based on Ti:sapphire laser are reviewed,including photoconductive antennas(PCAs),optical rectification sources,plasma-based THz sources,and some novel techniques for THz generations,such as topological insulators,spintronic materials,and metasurfaces.The coherent THz detection methods are summarized,and their limitations for intense THz detection are analyzed.Applications of intense THz radiation are introduced,including applications in spectroscopy detection,nonlinear effects,and switching of coherent magnons.The review is concluded with a short perspective on the generation and applications of intense THz radiation.展开更多
Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the t...Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the technical instruments to form and evaluate such beams are rather limited,as they are mainly collected in the visible range.The emergence of coded metasurfaces has reinvigorated the design of functional devices with multiple degrees of freedom.Here,we demonstrate a versatile design inspired by a binary encoding approach for generating off-axis vectorial THz beams on all-silicon metasurfaces.Experimentally,simultaneous manipulation of the encoding method within the orthogonal circularly polarized(CP)channel provides strong support for developing versatility in vector THz beams,including the generation of arbitrary polarization profiles and the directional emission of multiplexed vector vortex beams(VVBs)with specified polarization states.The introduction of the latitudinal polarization control factor guarantees that continuously rotating or independently designed vector polarization profiles can be obtained on a pre-defined focal plane.Subsequently,a universal parametric theoretical model is developed to analyze the evolutionary trend of off-axis VVB in detail.Notably,the proposed monolayer vector metasurface bypasses the requirement of multiple cascaded optical elements,further inducing the advancement of ultra-thin vector THz sources,and also facilitating the generation of vector fields with tailored polarization distributions in 3D space.展开更多
Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindepende...Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindependently tunable pixels and low modulation depth due to the ultra-small thickness of graphene.Here,we demonstrate a reconfigurable THz phase modulator with 5×5 independently tunable units enabled by switching the voltages applied on 10 graphene ribbons prepared by laser cutting.In addition,by introducing quasibound states in the continuum resonance through a designed double C-shaped antenna,the efficiency of the device is enhanced by 2.7–3.6 times under different graphene chemical potentials.Experimental results demonstrate that a focus can be formed,and the focal length is changed from 14.3 mm to 22.6 mm.This work provides potential for compact THz spatial light modulators that may be applied in THz communication,detection,and imaging.展开更多
The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication.Nonetheless,the development of compact and versatile polarization detection devices capable of...The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication.Nonetheless,the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor.Here,we demonstrate a terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field.The power of the proposed polarization recognition is verified by using three polarization trajectories,including linear polarizations,circular polarizations,and elliptical polarizations.Using the reconstructed complete polarization parameters,the detected polarization states are characterized using polarization ellipses,Poincarésphere,and full-Stokes parameters.The experimental results validate the power of this scheme in polarization detection.This scheme holds promise for applications in polarization imaging and terahertz communication.展开更多
Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To ...Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To be applied more widely, active metasurface devices are highly desired. Here, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ～4.45λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 to 12.24 mm when the gate voltage increases from 0 to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.展开更多
Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands.However,it is difficult to shape the beam with multi-channe...Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands.However,it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface.Here,we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface,which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms.By superimposing the eigen-and non-eigen-polarization responses of the two kinds of meta-atoms,we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves.The measured polarization conversion efficiency is higher than 70%in the range of 0.9–1.3 THz,with a peak value of 89.2%at 1.1 THz.In addition,when more other polarization states are incident,combined with the integration of sub-arrays,we can get more channels for both polarization conversion and beam shaping.Simulated and experimental results verify the feasibility of this method.The proposed method provides a new idea for the design of terahertz multi-functional metadevices.展开更多
Chiral metasurfaces based on asymmetric meta-atoms have achieved artificial circular dichroism(CD),spin-dependent wavefront control,near-field imaging,and other spin-related electromagnetic control.In this paper,we pr...Chiral metasurfaces based on asymmetric meta-atoms have achieved artificial circular dichroism(CD),spin-dependent wavefront control,near-field imaging,and other spin-related electromagnetic control.In this paper,we propose and experimentally verify a scheme for achieving high-efficiency chiral response similar to CD of terahertz(THz)wave via phase manipulation.By introducing the geometric phase and dynamic phase in an all-silicon metasurface,the spin-decoupled terahertz transmission is obtained.The giant circular dichroism-like effect in the transmission spectrum is observed by using a random phase distribution for one of the circular polarization components.More importantly,the effect can be adjusted when we change the area of the metasurface illuminated by an incident terahertz beam.In addition,we also demonstrate the spin-dependent arbitrary wavefront control of the transmitted terahertz wave,in which one of the circularly polarized components is scattered,while the other forms a focused vortex beam.Simulated and experimental results show that this method provides a new idea for spin selective control of THz waves.展开更多
Polarization is crucial in various fields such as imaging,sensing,and substance detection.A compact,fast,and accurate polarization detection device is vital for these applications.Herein,we demonstrate a multifocus me...Polarization is crucial in various fields such as imaging,sensing,and substance detection.A compact,fast,and accurate polarization detection device is vital for these applications.Herein,we demonstrate a multifocus metalens for terahertz polarization detection that requires only a single measurement to obtain complete polarization parameters and reconstruct the polarization state of the incident field.The individual subarrays of this metalens convert each of the six polarized components into the same polarization,which in turn links the Stokes parameters to these six foci.The incident linear polarizations and elliptical polarizations are characterized by Stokes parameters and polarization ellipses.Simulations and experimental results show that the scheme can accurately detect the incident polarization with a single measurement.The proposed metasurface polarimetry may find applications in the fields of real-time terahertz detection and integrated optics.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61675147,61735010 and 91838301)National Key Research and Development Program of China(No.2017YFA0700202)Basic Re-search Program of Shenzhen(JCYJ20170412154447469).
文摘If a metalens integrates the circular polarization(CP)conversion function,the focusing lens together with circular-polariz-ing lens(CPL)in traditional cameras may be replaced by a metalens.However,in terahertz(THz)band,the reported metalenses still do not obtain the perfect and strict single-handed CP,because they were constructed via Pancharatnam-Berry phase so that CP conversion contained both left-handed CP(LCP)and right-handed CP(RCP)components.In this paper,a silicon based THz metalens is constructed using dynamic phase to obtain single-handed CP conversion.Also,we can rotate the whole metalens at a certain angle to control the conversion of multi-polarization states,which can simply manipulate the focusing for incident linear polarization(LP)THz wave in three polarization conversion states,in-cluding LP without conversion,LCP and RCP.Moreover,the polarization conversion behavior is reversible,that is,the THz metalens can convert not only the LP into arbitrary single-handed CP,but also the LCP and RCP into two perpen-dicular LP,respectively.The metalens is expected to be used in advanced THz camera,as a great candidate for tradi-tional CPL and focusing lens group,and also shows potential application in polarization imaging with discriminating LCP and RCP.
文摘Metasurfaces that can realize the polarization manipulation of electromagnetic waves on the sub-wavelength scale have become an emerging research field.Here,a novel strategy of combining the metasurface and Fresnel zone plate to form a metasurface zone plate is proposed to realize the conversion from nearly arbitrary polarizations to a fixed polarization.Specifically,when one polarized wave is incident on adjacent ring zones constructed by different types of meta-atoms,the transmitted waves generated by odd-numbered and even-numbered ring zones converge at the same focus and superimpose to generate a fixed polarized wave.As function demonstrations,we have designed two types of metasurface zone plates:one is a focused linear polarizer,and the other can convert nearly arbitrary polarized waves into focused circularly polarized waves.The simulated and measured results are consistent with theoretical expectations,suggesting that the proposed concept is flexible and feasible.Our work provides an alternative platform for polarization manipulation and may vigorously promote the development of polarization photonic devices.
基金This work was supported by the National Key R&D Program of China(No.2019YFC1711905)the National Natural Science Foundation of China(Grant Nos.11774243,11774246,and 6167513)+2 种基金the Youth Innovative Research Team of Capital Normal University(No.19530050146)the Capacity Building for Science&Technology Innovation Fundamental Scientific Research Funds(Nos.19530050170 and 19530050180)the Scientific Research Base Development Program of the Beijing Municipal Commission of Education.
文摘Strong terahertz(THz)radiation provides a powerful tool to manipulate and control complex condensed matter systems.This review provides an overview of progress in the generation,detection,and applications of intense THz radiation.The tabletop intense THz sources based on Ti:sapphire laser are reviewed,including photoconductive antennas(PCAs),optical rectification sources,plasma-based THz sources,and some novel techniques for THz generations,such as topological insulators,spintronic materials,and metasurfaces.The coherent THz detection methods are summarized,and their limitations for intense THz detection are analyzed.Applications of intense THz radiation are introduced,including applications in spectroscopy detection,nonlinear effects,and switching of coherent magnons.The review is concluded with a short perspective on the generation and applications of intense THz radiation.
基金supported by the National Key Research and Development Program of China(2021YFB2800703 and 2017YFA0700202)the National Natural Science Foundation of China(61675147)Sichuan Science and Technology Program(2021ZYD0039)。
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFB2800703,and 2017YFA0700202)the National Natural Science Foundation of China(Grant Nos.61675147,61975146,62075159,62105240,and 91838301).
文摘Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the technical instruments to form and evaluate such beams are rather limited,as they are mainly collected in the visible range.The emergence of coded metasurfaces has reinvigorated the design of functional devices with multiple degrees of freedom.Here,we demonstrate a versatile design inspired by a binary encoding approach for generating off-axis vectorial THz beams on all-silicon metasurfaces.Experimentally,simultaneous manipulation of the encoding method within the orthogonal circularly polarized(CP)channel provides strong support for developing versatility in vector THz beams,including the generation of arbitrary polarization profiles and the directional emission of multiplexed vector vortex beams(VVBs)with specified polarization states.The introduction of the latitudinal polarization control factor guarantees that continuously rotating or independently designed vector polarization profiles can be obtained on a pre-defined focal plane.Subsequently,a universal parametric theoretical model is developed to analyze the evolutionary trend of off-axis VVB in detail.Notably,the proposed monolayer vector metasurface bypasses the requirement of multiple cascaded optical elements,further inducing the advancement of ultra-thin vector THz sources,and also facilitating the generation of vector fields with tailored polarization distributions in 3D space.
基金Beijing Municipal Natural Science Foundation (L223031)National Natural Science Foundation of China (61875010)。
文摘Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindependently tunable pixels and low modulation depth due to the ultra-small thickness of graphene.Here,we demonstrate a reconfigurable THz phase modulator with 5×5 independently tunable units enabled by switching the voltages applied on 10 graphene ribbons prepared by laser cutting.In addition,by introducing quasibound states in the continuum resonance through a designed double C-shaped antenna,the efficiency of the device is enhanced by 2.7–3.6 times under different graphene chemical potentials.Experimental results demonstrate that a focus can be formed,and the focal length is changed from 14.3 mm to 22.6 mm.This work provides potential for compact THz spatial light modulators that may be applied in THz communication,detection,and imaging.
基金China Postdoctoral Science Foundation(2023TQ0296)Excellent Youth Foundation of Henan Scientific Committee(232300421076)National Natural Science Foundation of China(12174350)。
文摘The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication.Nonetheless,the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor.Here,we demonstrate a terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field.The power of the proposed polarization recognition is verified by using three polarization trajectories,including linear polarizations,circular polarizations,and elliptical polarizations.Using the reconstructed complete polarization parameters,the detected polarization states are characterized using polarization ellipses,Poincarésphere,and full-Stokes parameters.The experimental results validate the power of this scheme in polarization detection.This scheme holds promise for applications in polarization imaging and terahertz communication.
基金National Key R&D Program of China(2017YFB1002900)973 Program of China(2013CBA01702)+1 种基金National Natural Science Foundation of China(NSFC)(11404224,1174243,11774246,61405012,61420106014)Excellent Young Scholars Research Fund of Beijing Institute of Technology(BIT)
文摘Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To be applied more widely, active metasurface devices are highly desired. Here, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ～4.45λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 to 12.24 mm when the gate voltage increases from 0 to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.
基金National Natural Science Foundation of China(61675147,61735010,91838301)National Key Research and Development Program of China(2017YFA0700202)Basic Research Program of Shenzhen(JCYJ20170412154447469).
文摘Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands.However,it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface.Here,we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface,which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms.By superimposing the eigen-and non-eigen-polarization responses of the two kinds of meta-atoms,we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves.The measured polarization conversion efficiency is higher than 70%in the range of 0.9–1.3 THz,with a peak value of 89.2%at 1.1 THz.In addition,when more other polarization states are incident,combined with the integration of sub-arrays,we can get more channels for both polarization conversion and beam shaping.Simulated and experimental results verify the feasibility of this method.The proposed method provides a new idea for the design of terahertz multi-functional metadevices.
基金Basic Research Program of Shenzhen(JCYJ20170412154447469)National Key Research and Development Program of China(2017YFA0700202)National Natural Science Foundation of China(61675147,61735010,91838301).
文摘Chiral metasurfaces based on asymmetric meta-atoms have achieved artificial circular dichroism(CD),spin-dependent wavefront control,near-field imaging,and other spin-related electromagnetic control.In this paper,we propose and experimentally verify a scheme for achieving high-efficiency chiral response similar to CD of terahertz(THz)wave via phase manipulation.By introducing the geometric phase and dynamic phase in an all-silicon metasurface,the spin-decoupled terahertz transmission is obtained.The giant circular dichroism-like effect in the transmission spectrum is observed by using a random phase distribution for one of the circular polarization components.More importantly,the effect can be adjusted when we change the area of the metasurface illuminated by an incident terahertz beam.In addition,we also demonstrate the spin-dependent arbitrary wavefront control of the transmitted terahertz wave,in which one of the circularly polarized components is scattered,while the other forms a focused vortex beam.Simulated and experimental results show that this method provides a new idea for spin selective control of THz waves.
基金China Postdoctoral Science Foundation(2023TQ0296)Excellent Youth Foundation of Henan Scientific Committee(232300421076)National Natural Science Foundation of China(12174350)。
文摘Polarization is crucial in various fields such as imaging,sensing,and substance detection.A compact,fast,and accurate polarization detection device is vital for these applications.Herein,we demonstrate a multifocus metalens for terahertz polarization detection that requires only a single measurement to obtain complete polarization parameters and reconstruct the polarization state of the incident field.The individual subarrays of this metalens convert each of the six polarized components into the same polarization,which in turn links the Stokes parameters to these six foci.The incident linear polarizations and elliptical polarizations are characterized by Stokes parameters and polarization ellipses.Simulations and experimental results show that the scheme can accurately detect the incident polarization with a single measurement.The proposed metasurface polarimetry may find applications in the fields of real-time terahertz detection and integrated optics.
