Terahertz metamaterial biosensors have attracted significant attention in the biological field due to their advantages of label-free,real-time and in situ detection.In this paper,a highly sensitive metamaterial sensor...Terahertz metamaterial biosensors have attracted significant attention in the biological field due to their advantages of label-free,real-time and in situ detection.In this paper,a highly sensitive metamaterial sensor with semi-ring mirror symmetry based on toroidal dipole resonance is designed for a new metamaterial biosensor.It is shown that a refractive index sensitivity of 337.5 GHz per refractive index unit can be achieved under an analyte of saturated thickness near a 1.33 THz transmission dip.For biosensor samples where aflatoxin B1 is dropped on the metamaterial surface in our experiment,dip amplitudes of transmission varying from 0.1904 to 0.203 and 0.2093 are observed as aflatoxin B1 concentrations are altered from 0 to 0.001μg·ml-1 and to 0.01μg·ml-1,respectively.Furthermore,when aflatoxin B1 concentrations are 0.1μg·ml-1,1μg·ml-1,10μg·ml-1 and 100μg·ml-1,dip amplitudes of 0.2179,0.226,0.2384 and 0.2527 and dip redshifts of 10.1 GHz,20.1 GHz,27.7 GHz and 37.6 GHz are respectively observed.These results illustrate high-sensitivity,label-free detection of aflatoxin B1,enriching the applications of sensors in the terahertz domain.展开更多
Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales.Recent advancements have focused on toroidal dipole(TD) and quasi-bound state in the continuum(quasi-BIC) modes,w...Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales.Recent advancements have focused on toroidal dipole(TD) and quasi-bound state in the continuum(quasi-BIC) modes,which are particularly attractive due to their capacity to enhance light-matter interaction.However,most metasurfaces with TD and quasi-BIC modes exhibit passive electromagnetic responses after fabrication,limiting their practical applications.This study presents both numerical and experimental investigations that demonstrate the active control of TD and quasi-BIC modes through the integration of symmetric and asymmetric aluminum dumbbell aperture arrays with the phase-change material Ge2Sb2Te5(GST).The symmetric hybrid dumbbell aperture array shows a pronounced TD response within the terahertz frequency range.In contrast,modifying the geometric parameters to disrupt the structural symmetry induces a quasi-BIC mode in the asymmetric hybrid dumbbell aperture array.Furthermore,as GST undergoes a phase transition from its amorphous to crystalline state,both TD and quasi-BIC modes become dynamically tunable,driven by changes in the conductivity of GST.Notably,significant modulation of the transmitted terahertz wave occurs around the frequencies corresponding to the TD and quasi-BIC modes during the GST phase transition.Symmetric and asymmetric hybrid dumbbell aperture arrays provide a versatile platform for generating tunable TD and quasi-BIC modes,with promising applications in terahertz modulators and filters.展开更多
Circular dichroism(CD)spectroscopy,widely used for chiral sensing,has been limited by the detection sensitivity.Enhancing optical chirality in the light fields interacting with chiral molecules is crucial for achievin...Circular dichroism(CD)spectroscopy,widely used for chiral sensing,has been limited by the detection sensitivity.Enhancing optical chirality in the light fields interacting with chiral molecules is crucial for achieving ultrasensitive chiral detection.Here,we present a new paradigm for ultrasensitive chiral detection by creating accessible chiral hotspots using a toroidal dipole Fabry–Perot bound state in the continuum(TD FP-BIC)metasurface.BIC resonance is achieved by controlling the coupling between the TD resonance and its multilayer reflector-induced perfect mirror image.This method enables unprecedented local maximum and average optical chirality enhancements of up to 6×10^(4)-fold and 2×10^(3)-fold,respectively,within non-structured regions,resulting in an 866-fold increase in CD signals compared to chiral molecules alone without nanostructures.Our results pave the way for enhanced light–matter interactions and ultrasensitive enantiomeric operation.展开更多
Colloidal metal nanocrystals(NCs)show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic properties.Herein,unique Au rod-cup NCs,where Au nanocups are embedded ...Colloidal metal nanocrystals(NCs)show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic properties.Herein,unique Au rod-cup NCs,where Au nanocups are embedded on the one or two ends of Au nanorods(NRs),are successfully prepared for the first time via a controllable wet-chemistry strategy.The Au rod-cup NCs possess multiple plasmon modes including transverse and longitudinal electric dipole(TED and LED),magnetic dipole(MD),and toroidal dipole(TD)modulated LED resonances,producing large extinction cross-section and huge near-field enhancements for plasmon-enhanced spectroscopy.Particularly,Au rod-cup NCs with two embedded cups show excellent surface-enhanced Raman spectroscopy(SERS)performance than Au NRs(75.6-fold enhancement excited at 633 nm)on detecting crystal violet owing to the strong electromagnetic hotspots synergistically induced by MD,LED,and TED-based plasmon coupling between Au cup and rod.Moreover,the strong TD-modulated dipole-dipole double-resonance and MD modes in Au rod-cup NCs bring a 37.3-fold enhancement of second-harmonic generation intensity compared with bare Au NRs,because they can efficiently harvest photoenergy at fundamental frequency and generate large near-field enhancements at second-harmonic wavelength.These findings provide a strategy for designing optical nanoantennas for plasmon-enhanced applications based on multiple plasmon modes.展开更多
Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and magnetic multipole distributions.Because of its special properties,the toroidal dipole is a rese...Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and magnetic multipole distributions.Because of its special properties,the toroidal dipole is a research hotspot in the field of metamaterials and nanophotonics.However,the low scattering of the toroidal dipole moment makes its excitation a challenging task.At present,there are relatively few studies on its specific engineering applications.In this paper,by slotting in the rectangular cavity,the excitation of an equivalent toroidal dipole is successfully achieved over a wide frequency range of 53-58 GHz.Results indicate that under the action of the toroidal dipole,the TE_(10)mode electromagnetic waves transmitted in the rectangular waveguide are converted into vector beams and are radiated outwards.Further adjusting the spatial distribution of the magnetic dipoles in the toroidal dipoles yields results that indicate that the resonance mode in the slot is still dominated by the magnetic toroidal dipole moment,and the electromagnetic waves radiating outward are vortex beams carrying vector polarization.The scattered energy of each dipole moment inside the antenna is calculated.This calculation verifies that the mass of the vector beam and vector vortex beam is closely related to the toroidal dipole supported by this antenna.The proposed structure can be applied to explorations in vortex filtering,in photon entanglement,and in the photonic spin Hall effect.展开更多
We theoretically study the near-field couplings of two stacked all-dielectric nanodisks,where each disk has an electric anapole mode consisting of an electric dipole mode and an electric toroidal dipole(ETD)mode.Stron...We theoretically study the near-field couplings of two stacked all-dielectric nanodisks,where each disk has an electric anapole mode consisting of an electric dipole mode and an electric toroidal dipole(ETD)mode.Strong bonding and anti-bonding hybridizations of the ETD modes of the two disks occur.The bonding hybridized ETD can interfere with the dimer’s electric dipole mode and induce a new electric anapole mode.The anti-bonding hybridization of the ETD modes can induce a magnetic toroidal dipole(MTD)response in the disk dimer.The MTD and magnetic dipole resonances of the dimer form a magnetic anapole mode.Thus,two dips associated with the hybridized modes appear on the scattering spectrum of the dimer.Furthermore,the MTD mode is also accompanied by an electric toroidal quadrupole mode.The hybridizations of the ETD and the induced higher-order modes can be adjusted by varying the geometries of the disks.The strong anapole mode couplings and the corresponding rich higher-order mode responses in simple all-dielectric nanostructures can provide new opportunities for nanoscale optical manipulations.展开更多
In recent years,continuous bound states in the continuum(BIC)have gained significant attention for their practical applications in optics,chip technology,and modern communication.Traditional approaches to realizing an...In recent years,continuous bound states in the continuum(BIC)have gained significant attention for their practical applications in optics,chip technology,and modern communication.Traditional approaches to realizing and analyzing BIC typi-cally rely on magnetic dipole models,which have limitations in quantitative analysis and integration.This creates a gap in understanding how to efficiently harness BIC with higher Q-factors for enhanced performance in real-world applications,particularly in scenarios involving terahertz imaging and multi-channel communication.In this study,we introduce a novel approach using a metallic resonator model that leverages toroidal dipole moments to generate symmetry-protected BIC with high Q-factors.By systematically varying the asymmetry parameters of the metasurface,we gradually break its symmetry,achieving a transition from the BIC mode to the quasi-BIC mode and facilitating the gradual release of stored electromag-netic energy.Our theoretical analysis confirms the existence and generation of BIC,and experimental measurements of the transmission response spectrum validate these theoretical predictions.The results indicate that terahertz metasurface with high Q-factors can produce strong resonances at specific frequencies,enhancing resistance to electromagnetic interference and ensuring stable imaging quality in complex environments.Additionally,this study suggests the potential for an integrated plasmonic ruler to achieve high-resolution and efficient biological imaging.These findings bridge the gap by demonstrating how high Q-factor BIC can be effectively utilized for multi-channel terahertz dynamic imaging and biosensing applications.This advancement lays a new foundation for developing robust systems in multi-channel communication and biomedical sensing,offering significant potential for future technological and medical innovations.展开更多
Optical metasurfaces to perform optical analog spatial differentiation operations and image edge detection processing is a currently hot topic.However,some metasurface differentiators are limited by polarization depen...Optical metasurfaces to perform optical analog spatial differentiation operations and image edge detection processing is a currently hot topic.However,some metasurface differentiators are limited by polarization dependence,narrow operating bandwidth,low numerical aperture(NA),requiring for additional polarization elements or digital processing,and under coherent light illumination conditions.Here,we use the optical angular dispersion effect based on resonant dielectric metasurface,to realize the Laplacian differential operation in the real space directly,which can address these critical metrics for p-and s-polarized light.Moreover,the broadband operating range of the metasurface differentiator can be obtained by exciting and detuning the electric toroidal dipole(ETD)and magnetic toroidal dipole(MTD)resonances.We experimentally demonstrate that azimuthal-insensitive Laplace differential operations and dual-polarization second-order two-dimensional edge detection with NA up to 0.64 and spectral bandwidths of nearly 100 nm from 750 to 850 nm.In addition,broadband incoherent and unpolarized edge detection experiments are also carried out with satisfactory performance.Our work will pave the way for free-space realization of high-efficiency,broadband parallel optical-computation and image-processing in machine-vision,biomedical,and optical microscopy.展开更多
Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments.The high quality anapole-related reso...Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments.The high quality anapole-related resonances can be used in enhancing nonlinear electromagnetic properties of materials and in sensor applications.In this work,we experimentally demonstrate plasmonic anapole metamaterial sensor of environmental refractive index in the optical part of the spectrum.Our results show that the sensor exhibits high sensitivity to the ambient refractive index at the level of 330 nm/RIU and noise floor of 8.7×10^(-5)RIU.This work will pave the way for applications of anapole metamaterials in biosensing and spectroscopy.展开更多
High-quality-factor(high-Q-factor)electromagnetic resonance plays an important role in sensor applications.Previously proposed gas refractive index sensors are often limited by the large cavity length or microscale fa...High-quality-factor(high-Q-factor)electromagnetic resonance plays an important role in sensor applications.Previously proposed gas refractive index sensors are often limited by the large cavity length or microscale fabrication process in practical applications.Recently,ultra-high Q factor resonance based on the bound state in the continuum(BIC)has provided a feasible approach to solve these problems.In this paper,we propose a metasurface structure consisting of a single size tetramer cylinder.It supports dual band toroidal dipole(TD)resonances driven by BIC.The physical mechanism of double TD resonances is clarified by the multipole decomposition of the metasurface band structure and far-field scattering power.The sensor structure based on this achieves a sensitivity of 518.3 MHz/RIU,and the maximum line width does not exceed 680kHz.The high-Q-factor electromagnetic resonance has the advantages of polarization independence and simplicity to manufacture.These findings will open up an avenue to develop the ultrasensitive sensor in the gigahertz regime.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61927813,61865009,and 12104203)Jiangxi Provincial Natural Science Foundation(Grant No.20212ACB201007).
文摘Terahertz metamaterial biosensors have attracted significant attention in the biological field due to their advantages of label-free,real-time and in situ detection.In this paper,a highly sensitive metamaterial sensor with semi-ring mirror symmetry based on toroidal dipole resonance is designed for a new metamaterial biosensor.It is shown that a refractive index sensitivity of 337.5 GHz per refractive index unit can be achieved under an analyte of saturated thickness near a 1.33 THz transmission dip.For biosensor samples where aflatoxin B1 is dropped on the metamaterial surface in our experiment,dip amplitudes of transmission varying from 0.1904 to 0.203 and 0.2093 are observed as aflatoxin B1 concentrations are altered from 0 to 0.001μg·ml-1 and to 0.01μg·ml-1,respectively.Furthermore,when aflatoxin B1 concentrations are 0.1μg·ml-1,1μg·ml-1,10μg·ml-1 and 100μg·ml-1,dip amplitudes of 0.2179,0.226,0.2384 and 0.2527 and dip redshifts of 10.1 GHz,20.1 GHz,27.7 GHz and 37.6 GHz are respectively observed.These results illustrate high-sensitivity,label-free detection of aflatoxin B1,enriching the applications of sensors in the terahertz domain.
基金National Natural Science Foundation of China(12304434, 12304433, 12204446, 12004361, 12004362)Natural Science Foundation of Zhejiang Province(LY22A040006)+1 种基金Fundamental Research Funds for the Provincial Universities of Zhejiang (2023YW06,2023YW01)State Key Laboratory of Millimeter Waves(K202429)
文摘Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales.Recent advancements have focused on toroidal dipole(TD) and quasi-bound state in the continuum(quasi-BIC) modes,which are particularly attractive due to their capacity to enhance light-matter interaction.However,most metasurfaces with TD and quasi-BIC modes exhibit passive electromagnetic responses after fabrication,limiting their practical applications.This study presents both numerical and experimental investigations that demonstrate the active control of TD and quasi-BIC modes through the integration of symmetric and asymmetric aluminum dumbbell aperture arrays with the phase-change material Ge2Sb2Te5(GST).The symmetric hybrid dumbbell aperture array shows a pronounced TD response within the terahertz frequency range.In contrast,modifying the geometric parameters to disrupt the structural symmetry induces a quasi-BIC mode in the asymmetric hybrid dumbbell aperture array.Furthermore,as GST undergoes a phase transition from its amorphous to crystalline state,both TD and quasi-BIC modes become dynamically tunable,driven by changes in the conductivity of GST.Notably,significant modulation of the transmitted terahertz wave occurs around the frequencies corresponding to the TD and quasi-BIC modes during the GST phase transition.Symmetric and asymmetric hybrid dumbbell aperture arrays provide a versatile platform for generating tunable TD and quasi-BIC modes,with promising applications in terahertz modulators and filters.
基金National Key Research and Development Program of China(2023YFF0615604)National Natural Science Foundation of China(62192770,62305252,62205246,62475192,61925504,62020106009,62192771)+3 种基金Science and Technology Commission of Shanghai Municipality(21JC1406100,22ZR1432400)Shanghai Municipal Science and Technology Major Project(2021SHZDZX0100)Shanghai Pilot Program for Basic ResearchFundamental Research Funds for the Central Universities。
文摘Circular dichroism(CD)spectroscopy,widely used for chiral sensing,has been limited by the detection sensitivity.Enhancing optical chirality in the light fields interacting with chiral molecules is crucial for achieving ultrasensitive chiral detection.Here,we present a new paradigm for ultrasensitive chiral detection by creating accessible chiral hotspots using a toroidal dipole Fabry–Perot bound state in the continuum(TD FP-BIC)metasurface.BIC resonance is achieved by controlling the coupling between the TD resonance and its multilayer reflector-induced perfect mirror image.This method enables unprecedented local maximum and average optical chirality enhancements of up to 6×10^(4)-fold and 2×10^(3)-fold,respectively,within non-structured regions,resulting in an 866-fold increase in CD signals compared to chiral molecules alone without nanostructures.Our results pave the way for enhanced light–matter interactions and ultrasensitive enantiomeric operation.
基金funded by the National Natural Science Foundation of China(Nos.11904270 and 11904332)Hubei Key Laboratory of Optical Information and Pattern Recognition(Nos.202004 and 202010),Wuhan Institute of Technology.
文摘Colloidal metal nanocrystals(NCs)show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic properties.Herein,unique Au rod-cup NCs,where Au nanocups are embedded on the one or two ends of Au nanorods(NRs),are successfully prepared for the first time via a controllable wet-chemistry strategy.The Au rod-cup NCs possess multiple plasmon modes including transverse and longitudinal electric dipole(TED and LED),magnetic dipole(MD),and toroidal dipole(TD)modulated LED resonances,producing large extinction cross-section and huge near-field enhancements for plasmon-enhanced spectroscopy.Particularly,Au rod-cup NCs with two embedded cups show excellent surface-enhanced Raman spectroscopy(SERS)performance than Au NRs(75.6-fold enhancement excited at 633 nm)on detecting crystal violet owing to the strong electromagnetic hotspots synergistically induced by MD,LED,and TED-based plasmon coupling between Au cup and rod.Moreover,the strong TD-modulated dipole-dipole double-resonance and MD modes in Au rod-cup NCs bring a 37.3-fold enhancement of second-harmonic generation intensity compared with bare Au NRs,because they can efficiently harvest photoenergy at fundamental frequency and generate large near-field enhancements at second-harmonic wavelength.These findings provide a strategy for designing optical nanoantennas for plasmon-enhanced applications based on multiple plasmon modes.
基金supported by the National Key R&D Program of China(No.2021YFC290202)the National Natural Science Foundation of China(No.51874301)the Primary Research&Development Plan of Xuzhou City(No.KC20162)。
文摘Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and magnetic multipole distributions.Because of its special properties,the toroidal dipole is a research hotspot in the field of metamaterials and nanophotonics.However,the low scattering of the toroidal dipole moment makes its excitation a challenging task.At present,there are relatively few studies on its specific engineering applications.In this paper,by slotting in the rectangular cavity,the excitation of an equivalent toroidal dipole is successfully achieved over a wide frequency range of 53-58 GHz.Results indicate that under the action of the toroidal dipole,the TE_(10)mode electromagnetic waves transmitted in the rectangular waveguide are converted into vector beams and are radiated outwards.Further adjusting the spatial distribution of the magnetic dipoles in the toroidal dipoles yields results that indicate that the resonance mode in the slot is still dominated by the magnetic toroidal dipole moment,and the electromagnetic waves radiating outward are vortex beams carrying vector polarization.The scattered energy of each dipole moment inside the antenna is calculated.This calculation verifies that the mass of the vector beam and vector vortex beam is closely related to the toroidal dipole supported by this antenna.The proposed structure can be applied to explorations in vortex filtering,in photon entanglement,and in the photonic spin Hall effect.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704416 and 11704107)the Hunan Provincial Natural Science Foundation of China(Grant No.2021JJ20076)the Hubei Provincial Natural Science Foundation of China(Grant No.2020CFB557)。
文摘We theoretically study the near-field couplings of two stacked all-dielectric nanodisks,where each disk has an electric anapole mode consisting of an electric dipole mode and an electric toroidal dipole(ETD)mode.Strong bonding and anti-bonding hybridizations of the ETD modes of the two disks occur.The bonding hybridized ETD can interfere with the dimer’s electric dipole mode and induce a new electric anapole mode.The anti-bonding hybridization of the ETD modes can induce a magnetic toroidal dipole(MTD)response in the disk dimer.The MTD and magnetic dipole resonances of the dimer form a magnetic anapole mode.Thus,two dips associated with the hybridized modes appear on the scattering spectrum of the dimer.Furthermore,the MTD mode is also accompanied by an electric toroidal quadrupole mode.The hybridizations of the ETD and the induced higher-order modes can be adjusted by varying the geometries of the disks.The strong anapole mode couplings and the corresponding rich higher-order mode responses in simple all-dielectric nanostructures can provide new opportunities for nanoscale optical manipulations.
基金sponsored by National Natural Science Foundation of China(12104339,62101078).
文摘In recent years,continuous bound states in the continuum(BIC)have gained significant attention for their practical applications in optics,chip technology,and modern communication.Traditional approaches to realizing and analyzing BIC typi-cally rely on magnetic dipole models,which have limitations in quantitative analysis and integration.This creates a gap in understanding how to efficiently harness BIC with higher Q-factors for enhanced performance in real-world applications,particularly in scenarios involving terahertz imaging and multi-channel communication.In this study,we introduce a novel approach using a metallic resonator model that leverages toroidal dipole moments to generate symmetry-protected BIC with high Q-factors.By systematically varying the asymmetry parameters of the metasurface,we gradually break its symmetry,achieving a transition from the BIC mode to the quasi-BIC mode and facilitating the gradual release of stored electromag-netic energy.Our theoretical analysis confirms the existence and generation of BIC,and experimental measurements of the transmission response spectrum validate these theoretical predictions.The results indicate that terahertz metasurface with high Q-factors can produce strong resonances at specific frequencies,enhancing resistance to electromagnetic interference and ensuring stable imaging quality in complex environments.Additionally,this study suggests the potential for an integrated plasmonic ruler to achieve high-resolution and efficient biological imaging.These findings bridge the gap by demonstrating how high Q-factor BIC can be effectively utilized for multi-channel terahertz dynamic imaging and biosensing applications.This advancement lays a new foundation for developing robust systems in multi-channel communication and biomedical sensing,offering significant potential for future technological and medical innovations.
基金funding provided by the National Key R&D Program of China(2021YFA1401200)the National Natural Science Foundation of China program(No.U21A20140)+1 种基金the National Science Fund for Distinguished Young Scholars(No.52325505)the Beijing Natural Science Foundation(JQ24028).
文摘Optical metasurfaces to perform optical analog spatial differentiation operations and image edge detection processing is a currently hot topic.However,some metasurface differentiators are limited by polarization dependence,narrow operating bandwidth,low numerical aperture(NA),requiring for additional polarization elements or digital processing,and under coherent light illumination conditions.Here,we use the optical angular dispersion effect based on resonant dielectric metasurface,to realize the Laplacian differential operation in the real space directly,which can address these critical metrics for p-and s-polarized light.Moreover,the broadband operating range of the metasurface differentiator can be obtained by exciting and detuning the electric toroidal dipole(ETD)and magnetic toroidal dipole(MTD)resonances.We experimentally demonstrate that azimuthal-insensitive Laplace differential operations and dual-polarization second-order two-dimensional edge detection with NA up to 0.64 and spectral bandwidths of nearly 100 nm from 750 to 850 nm.In addition,broadband incoherent and unpolarized edge detection experiments are also carried out with satisfactory performance.Our work will pave the way for free-space realization of high-efficiency,broadband parallel optical-computation and image-processing in machine-vision,biomedical,and optical microscopy.
基金supported by the UK Engineering and Physical Science Research Council(grants EP/M009122/1 and EP/T02643X/1)the Royal Society(grant IEC/R3/170092)+6 种基金the European Research Council(Advanced Grant No.FLEET-786851)the Singapore Ministry of Education(N.I.Z.grant MOE2016-T3-1-006)the University Grants Committee/Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.AoE/P-502/20 and GRF Project:15303521)the Shenzhen Science and Technology Innovation Commission(Grant No.SGDX2019081623281169)the Department of Science and Technology of Guangdong Province(2020B1515120073)the City University of Hong Kong(Grant No.9380131).
文摘Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments.The high quality anapole-related resonances can be used in enhancing nonlinear electromagnetic properties of materials and in sensor applications.In this work,we experimentally demonstrate plasmonic anapole metamaterial sensor of environmental refractive index in the optical part of the spectrum.Our results show that the sensor exhibits high sensitivity to the ambient refractive index at the level of 330 nm/RIU and noise floor of 8.7×10^(-5)RIU.This work will pave the way for applications of anapole metamaterials in biosensing and spectroscopy.
基金supported in part by the National Natural Science Foundation of China(Grant No.11811530052)Intergovernmental Scienceand Technology Regular Meeting Exchange Project of Ministry of Science and Technology of China(Grant No.CB02-20)+1 种基金Open Fund of State Key Laboratory of Applied Optics(Grant No.SKLA02020001A04)Undergraduate Research and Innovation Projects of China(Grant No.2021102Z).
文摘High-quality-factor(high-Q-factor)electromagnetic resonance plays an important role in sensor applications.Previously proposed gas refractive index sensors are often limited by the large cavity length or microscale fabrication process in practical applications.Recently,ultra-high Q factor resonance based on the bound state in the continuum(BIC)has provided a feasible approach to solve these problems.In this paper,we propose a metasurface structure consisting of a single size tetramer cylinder.It supports dual band toroidal dipole(TD)resonances driven by BIC.The physical mechanism of double TD resonances is clarified by the multipole decomposition of the metasurface band structure and far-field scattering power.The sensor structure based on this achieves a sensitivity of 518.3 MHz/RIU,and the maximum line width does not exceed 680kHz.The high-Q-factor electromagnetic resonance has the advantages of polarization independence and simplicity to manufacture.These findings will open up an avenue to develop the ultrasensitive sensor in the gigahertz regime.
