The excellent mechanical properties make graphene promising for realizing nanomechanical resonators with high resonant frequencies,large quality factors,strong nonlinearities,and the capability to efectively interface...The excellent mechanical properties make graphene promising for realizing nanomechanical resonators with high resonant frequencies,large quality factors,strong nonlinearities,and the capability to efectively interface with various physical systems.Equipped with gate electrodes,it has been demonstrated that these exceptional device properties can be electrically manipulated,leading to a variety of nanomechanical/acoustic applications.Here,we review the recent progress of graphene nanomechanical resonators with a focus on their electrical tunability.First,we provide an overview of diferent graphene nanomechanical resonators,including their device structures,fabrication methods,and measurement setups.Then,the key mechanical properties of these devices,for example,resonant frequencies,nonlinearities,dissipations,and mode coupling mechanisms,are discussed,with their behaviors upon electrical gating being highlighted.After that,various potential classical/quantum applications based on these graphene nanomechanical resonators are reviewed.Finally,we briefy discuss challenges and opportunities in this feld to ofer future prospects for the ongoing studies on graphene nanomechanical resonators.展开更多
The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprisin...The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate(BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 d B or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of-2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.展开更多
The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is o...The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is of great importance not only to device physics but also to technological applications. Here we demonstrate a widely tunable bandgap of few-layer black phosphorus （BP） by the application of vertical electric field in dual-gated BP field-effect transistors. A total bandgap reduction of 124 meV is observed when the electrical displacement field is increased from 0.10 V/nm to 0.83 V/nm. Our results suggest appealing potential for few-layer BP as a tunable bandgap material in infrared optoelectronies, thermoelectric power generation and thermal imaging.展开更多
We theoretically and numerically demonstrate that a transmission-type electrically tunable polarizer can be realized by using graphene ribbons supported on a dielectric film with a graphene sheet behind. The polarizat...We theoretically and numerically demonstrate that a transmission-type electrically tunable polarizer can be realized by using graphene ribbons supported on a dielectric film with a graphene sheet behind. The polarization mechanism originates from the antenna plasmon resonance of graphene stripes. The results of full-wave numerical simulations reveal that transmittance of 0.70 for one polarization and 0.0073 for another polarization can be obtained at normal incidence. The transmission-type electrically tunable polarizer provides and facilitates a variety of applications, including filtering, detecting, and imaging.展开更多
An actively enhanced resonant transmission in a plasmonic array of subwavelength holes is demonstrated by use of terahertz time-domain spectroscopy. By connecting this two-dimensional element into an electrical circui...An actively enhanced resonant transmission in a plasmonic array of subwavelength holes is demonstrated by use of terahertz time-domain spectroscopy. By connecting this two-dimensional element into an electrical circuit, tunable resonance enhancement is observed in arrays made from good and relatively poor metals. The tunable feature is attributed to the nonlinear electric response of the periodic hole array film, which is confirmed by its voltage-current behavior. This finding could lead to a unique route to active plasmonic devices, such as tunable filters, spatial modulators, and integrated terahertz optoelectronic components.展开更多
Atomically thin semiconductors exhibit tunable exciton resonances that can be harnessed for dynamic manipulation of visible light in ultra-compact metadevices.However,the rapid nonradiative decay and dephasing of exci...Atomically thin semiconductors exhibit tunable exciton resonances that can be harnessed for dynamic manipulation of visible light in ultra-compact metadevices.However,the rapid nonradiative decay and dephasing of excitons at room temperature limit current active excitonic metasurfaces to a few-percent efficiencies.Here,we leverage the combined merits of pristine 2D heterostructures and non-local dielectric metasurfaces to enhance the excitonic lightmatter interaction,achieving strong and electrically tunable exciton-photon coupling at ambient conditions in a hybrid-2D excitonic metasurface.Using this,we realize a free-space optical modulator and experimentally demonstrate 9.9 dB of reflectance modulation.The electro-optic response,characterized by a continuous transition from strong to weak coupling,is mediated by gating-induced variations in the free carrier concentration,altering the exciton’s nonradiative decay rate.These results highlight how hybrid-2D excitonic metasurfaces offer novel opportunities to realize nanophotonic devices for active wavefront manipulation and optical communication.展开更多
We study electric currents in a piezoelectric semiconductor fiber under a constant voltage and time-dependent axial stresses applied locally.From a nonlinear numerical analysis based on a one-dimensional phenomenologi...We study electric currents in a piezoelectric semiconductor fiber under a constant voltage and time-dependent axial stresses applied locally.From a nonlinear numerical analysis based on a one-dimensional phenomenological model using the commercial software COMSOL,it is found that pulse electric currents can be produced by periodic or time-harmonic stresses.The pulse currents can be tuned by the amplitude and frequency of the applied stress.The result obtained provides a new approach for the mechanical control of electric currents in piezoelectric semiconductor fibers and has potential applications in piezotronics.展开更多
We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by e...We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.展开更多
In this Letter, we present a high-speed volumetric imaging system based on structured illumination and an electrically tunable lens（ETL）, where the ETL performs fast axial scanning at hundreds of Hz. In the system,a...In this Letter, we present a high-speed volumetric imaging system based on structured illumination and an electrically tunable lens（ETL）, where the ETL performs fast axial scanning at hundreds of Hz. In the system,a digital micro-mirror device（DMD） is utilized to rapidly generate structured images at the focal plane in synchronization with the axial scanning unit. The scanning characteristics of the ETL are investigated theoretically and experimentally. Imaging experiments on pollen samples are performed to verify the optical cross-sectioning and fast axial scanning capabilities. The results show that our system can perform fast axial scanning and threedimensional（3D） imaging when paired with a high-speed camera, presenting an economic solution for advanced biological imaging applications.展开更多
By using an optical system simulator, we investigated the tunable delay-line with an optical SSB modulator and an optical fiber loop, where the delay can be controlled by the electric signal fed to the modulator.
Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typicall...Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.展开更多
Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surface...Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surfaces of 2D materials enable the direct integration of different materials with various properties through van der Waals(vdW)forces into vdW heterostructures,providing new opportunities for constructing new type devices with superior performances.In this study,we report the vertical assembly of n-type CdS and p-type BP into p-n junctions.The electrically tunable heterojunction device shows a high current rectifying ratio up to8×103at a low bias voltage range of±1 V and an ideality factor of 1.5.More interestingly,the CdS/BP vdW heterojunction exhibits an ultra-high photoresponsivity up to 9.2×105A W-1and an ultra-high specific detectivity of 3.2×1013Jones with a low bias voltage of 1.0 V,which is among the highest in the reported results of 2D heterostructures.While operated at a self-powered mode,the device also exhibits excellent photodetection performances with a high photoresponsivity of0.27 A W-1and a high external quantum efficiency of 76%.Time-resolved photoresponse characterizations indicate that the device possesses a fast response time of about 10 ms.The developed CdS/BP vdW heterojunctions will find potential applications in the next-generation nanoscale electronics and optoelectronics applications.展开更多
Excitons dominate the photonic and optoelectronic properties of a material.Although significant advancements exist in understanding various types of excitons,progress on excitons that are indirect in both real-and mom...Excitons dominate the photonic and optoelectronic properties of a material.Although significant advancements exist in understanding various types of excitons,progress on excitons that are indirect in both real-and momentum-spaces is still limited.Here,we demonstrate the real-and momentum-indirect neutral and charged excitons(including their phonon replicas)in a multi-valley semiconductor of bilayer MoS_(2),by performing electric-field/doping-density dependent photoluminescence.Together with first-principles calculations,we uncover that the observed real-and momentum-indirect exciton involves electron/hole from K/Γvalley,solving the longstanding controversy of its momentum origin.Remarkably,the binding energy of real-and momentum-indirect charged exciton is extremely large(i.e.,~59 meV),more than twice that of real-and momentum-direct charged exciton(i.e.,~24 meV).The giant binding energy,along with the electrical tunability and long lifetime,endows real-and momentum-indirect excitons an emerging platform to study many-body physics and to illuminate developments in photonics and optoelectronics.展开更多
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20240123)the National Key Research and Development Program of China(Grant No.2022YFA1405900)the National Natural Science Foundation of China(Grant Nos.12274397,12274401,and 12034018)。
文摘The excellent mechanical properties make graphene promising for realizing nanomechanical resonators with high resonant frequencies,large quality factors,strong nonlinearities,and the capability to efectively interface with various physical systems.Equipped with gate electrodes,it has been demonstrated that these exceptional device properties can be electrically manipulated,leading to a variety of nanomechanical/acoustic applications.Here,we review the recent progress of graphene nanomechanical resonators with a focus on their electrical tunability.First,we provide an overview of diferent graphene nanomechanical resonators,including their device structures,fabrication methods,and measurement setups.Then,the key mechanical properties of these devices,for example,resonant frequencies,nonlinearities,dissipations,and mode coupling mechanisms,are discussed,with their behaviors upon electrical gating being highlighted.After that,various potential classical/quantum applications based on these graphene nanomechanical resonators are reviewed.Finally,we briefy discuss challenges and opportunities in this feld to ofer future prospects for the ongoing studies on graphene nanomechanical resonators.
基金supported by the Agency for Science, Technology and Research (A*STAR) under AME IRG Grant No. A2083c0058AME IAF-PP Grant No. 182 24 30030+1 种基金HBMS IAF-PP Grant No. H19H6a0025by MOE Tier 3 program LUNI170919a PUBMOE。
文摘The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate(BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 d B or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of-2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB921900 and 2014CB920900the National Natural Science Foundation of China under Grant No 11374021)(S.Yan,Z.Xie,J.-H,Chen)+1 种基金support from the Elemental Strategy Initiative conducted by the MEXT,Japana Grant-in-Aid for Scientific Research on Innovative Areas"Science of Atomic Layers"from JSPS
文摘The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is of great importance not only to device physics but also to technological applications. Here we demonstrate a widely tunable bandgap of few-layer black phosphorus （BP） by the application of vertical electric field in dual-gated BP field-effect transistors. A total bandgap reduction of 124 meV is observed when the electrical displacement field is increased from 0.10 V/nm to 0.83 V/nm. Our results suggest appealing potential for few-layer BP as a tunable bandgap material in infrared optoelectronies, thermoelectric power generation and thermal imaging.
基金Supported by the National Basic Research Program of China under Grant No 2012CB933501the National Natural Science Foundation of China under Grant Nos 61177051,11304389,61404174 and 61205087
文摘We theoretically and numerically demonstrate that a transmission-type electrically tunable polarizer can be realized by using graphene ribbons supported on a dielectric film with a graphene sheet behind. The polarization mechanism originates from the antenna plasmon resonance of graphene stripes. The results of full-wave numerical simulations reveal that transmittance of 0.70 for one polarization and 0.0073 for another polarization can be obtained at normal incidence. The transmission-type electrically tunable polarizer provides and facilitates a variety of applications, including filtering, detecting, and imaging.
基金supported by the National Natural Science Foundation of China(Grant No.61007034)
文摘An actively enhanced resonant transmission in a plasmonic array of subwavelength holes is demonstrated by use of terahertz time-domain spectroscopy. By connecting this two-dimensional element into an electrical circuit, tunable resonance enhancement is observed in arrays made from good and relatively poor metals. The tunable feature is attributed to the nonlinear electric response of the periodic hole array film, which is confirmed by its voltage-current behavior. This finding could lead to a unique route to active plasmonic devices, such as tunable filters, spatial modulators, and integrated terahertz optoelectronic components.
基金funded by a Vidi grant(VI.Vidi.203.027)from the Dutch National Science Foundation(NWO).
文摘Atomically thin semiconductors exhibit tunable exciton resonances that can be harnessed for dynamic manipulation of visible light in ultra-compact metadevices.However,the rapid nonradiative decay and dephasing of excitons at room temperature limit current active excitonic metasurfaces to a few-percent efficiencies.Here,we leverage the combined merits of pristine 2D heterostructures and non-local dielectric metasurfaces to enhance the excitonic lightmatter interaction,achieving strong and electrically tunable exciton-photon coupling at ambient conditions in a hybrid-2D excitonic metasurface.Using this,we realize a free-space optical modulator and experimentally demonstrate 9.9 dB of reflectance modulation.The electro-optic response,characterized by a continuous transition from strong to weak coupling,is mediated by gating-induced variations in the free carrier concentration,altering the exciton’s nonradiative decay rate.These results highlight how hybrid-2D excitonic metasurfaces offer novel opportunities to realize nanophotonic devices for active wavefront manipulation and optical communication.
基金This work was supported by the State Key Laboratory of Mechanics and Control of Mechanical Structures at NUAA[Grant number MCMS-E-0520K02]the Key Laboratory of Impact and Safety Engineering,Ministry of Education at Ningbo University[Grant number CJ201904]+1 种基金the Fundamental Research Funds for the Central Universities[Grant numbers NE2020002,NS2019007]a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘We study electric currents in a piezoelectric semiconductor fiber under a constant voltage and time-dependent axial stresses applied locally.From a nonlinear numerical analysis based on a one-dimensional phenomenological model using the commercial software COMSOL,it is found that pulse electric currents can be produced by periodic or time-harmonic stresses.The pulse currents can be tuned by the amplitude and frequency of the applied stress.The result obtained provides a new approach for the mechanical control of electric currents in piezoelectric semiconductor fibers and has potential applications in piezotronics.
基金supported by the Natural Science Foundation of Beijing under Grant No.4144069the Science and Technology Project of Beijing Municipal Education Commission under Grant No.KM201410028004
文摘We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.
基金supported by the National Natural Science Foundation of China(NSFC),General Program(No.51375415)the Development of a Flexure-based Optical Scanning System and a Multimodal Nonlinear Endomicroscope for in vivo Biological Studiesthe HKSAR Research Grants Council(RGC)General Research Fund(CUHK 14202815)
文摘In this Letter, we present a high-speed volumetric imaging system based on structured illumination and an electrically tunable lens（ETL）, where the ETL performs fast axial scanning at hundreds of Hz. In the system,a digital micro-mirror device（DMD） is utilized to rapidly generate structured images at the focal plane in synchronization with the axial scanning unit. The scanning characteristics of the ETL are investigated theoretically and experimentally. Imaging experiments on pollen samples are performed to verify the optical cross-sectioning and fast axial scanning capabilities. The results show that our system can perform fast axial scanning and threedimensional（3D） imaging when paired with a high-speed camera, presenting an economic solution for advanced biological imaging applications.
文摘By using an optical system simulator, we investigated the tunable delay-line with an optical SSB modulator and an optical fiber loop, where the delay can be controlled by the electric signal fed to the modulator.
基金supported by the POSCO-POSTECH-RIST Convergence Research Center program funded by POSCO,the Samsung Research Funding&Incubation Center for Future Technology grant(SRFC-IT1901-52)funded by Samsung Electronicsthe National Research Foundation(NRF)grants(NRF-2022M3C1A3081312,NRF-2022M3H4A1A-02074314,NRF-2022M3H4A1A02046445,NRF-2021M3H4A1A04086357,NRF-2019R1A5A8080290,RS-2024-00356928,RS-2023-00283667)funded by the Ministry of Science and ICT of the Korean governmentthe Korea Evaluation Institute of Industrial Technology(KEIT)grant(No.1415185027/20019169,Alchemist project)funded by the Ministry of Trade,Industry and Energy(MOTIE)of the Korean government.H.Kim and J.Kim acknowledge the POSTECH Alchemist fellowship,the Asan Foundation Biomedical Science fellowship,and Presidential Science fellowship funded by the MSIT of the Korean government.
文摘Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.
基金supported by the National Natural Science Foundation of China(U19A2090,51902098,51972105,51525202 and 61574054)Hunan Provincial Natural Science Foundation of China(2018RS3051)。
文摘Two-dimensional(2D)materials have recently received great attention for their atomic thin thickness and thus derived outstanding electrical,optical and optoelectronic properties.Moreover,the dangling-bond-free surfaces of 2D materials enable the direct integration of different materials with various properties through van der Waals(vdW)forces into vdW heterostructures,providing new opportunities for constructing new type devices with superior performances.In this study,we report the vertical assembly of n-type CdS and p-type BP into p-n junctions.The electrically tunable heterojunction device shows a high current rectifying ratio up to8×103at a low bias voltage range of±1 V and an ideality factor of 1.5.More interestingly,the CdS/BP vdW heterojunction exhibits an ultra-high photoresponsivity up to 9.2×105A W-1and an ultra-high specific detectivity of 3.2×1013Jones with a low bias voltage of 1.0 V,which is among the highest in the reported results of 2D heterostructures.While operated at a self-powered mode,the device also exhibits excellent photodetection performances with a high photoresponsivity of0.27 A W-1and a high external quantum efficiency of 76%.Time-resolved photoresponse characterizations indicate that the device possesses a fast response time of about 10 ms.The developed CdS/BP vdW heterojunctions will find potential applications in the next-generation nanoscale electronics and optoelectronics applications.
基金This work was supported by the National Natural Science Foundation of China(NSFC)(12274447,61888102,11834017,61734001,and 12074412)the National Key Research and Development Program(2021YFA1202900 and 2021YFA1400502)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)the Key-Area Research and Development Program of Guangdong Province(2020B0101340001).
文摘Excitons dominate the photonic and optoelectronic properties of a material.Although significant advancements exist in understanding various types of excitons,progress on excitons that are indirect in both real-and momentum-spaces is still limited.Here,we demonstrate the real-and momentum-indirect neutral and charged excitons(including their phonon replicas)in a multi-valley semiconductor of bilayer MoS_(2),by performing electric-field/doping-density dependent photoluminescence.Together with first-principles calculations,we uncover that the observed real-and momentum-indirect exciton involves electron/hole from K/Γvalley,solving the longstanding controversy of its momentum origin.Remarkably,the binding energy of real-and momentum-indirect charged exciton is extremely large(i.e.,~59 meV),more than twice that of real-and momentum-direct charged exciton(i.e.,~24 meV).The giant binding energy,along with the electrical tunability and long lifetime,endows real-and momentum-indirect excitons an emerging platform to study many-body physics and to illuminate developments in photonics and optoelectronics.
