Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer,monitoring treatm...Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer,monitoring treatment and detecting relapse.Here,a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial.By precisely engineering the configuration with atomically thin materials,the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect.Based on our knowledge,it is the first experimental demonstration of a lateral position signal change>340μm at a sensing interface from all optical techniques.With this enhanced plasmonic effect,the detection limit has been experimentally demonstrated to be 10^(-15) mol L^(−1) for TNF-α cancer marker,which has been found in various human diseases including inflammatory diseases and different kinds of cancer.The as-reported novel integration of atomically thin Ge_(2)Sb_(2)Te_(5) with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.展开更多
Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in prac...Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in practice,that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies.This opens up applications in computer-generated holography,allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography.We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two-and three-dimensional holographic objects.We show that phaseamplitude metasurfaces enable a few features not attainable in phase-only holography;these include creating artifactfree two-dimensional holographic images,encoding phase and amplitude profiles separately at the object plane,encoding intensity profiles at the metasurface and object planes separately,and controlling the surface textures of three-dimensional holographic objects.展开更多
Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging ...Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging systems and to realize new imaging modalities.However,it is a major challenge to create achromatic metalenses that produce a single focal length over a broad wavelength range because of the difficulty in simultaneously engineering phase profiles at distinct wavelengths on a single metasurface.For practical applications,there is a further challenge to create broadband achromatic metalenses that work in the transmission mode for incident light waves with any arbitrary polarization state.We developed a design methodology and created libraries of meta-units—building blocks of metasurfaces—with complex cross-sectional geometries to provide diverse phase dispersions(phase as a function of wavelength),which is crucial for creating broadband achromatic metalenses.We elucidated the fundamental limitations of achromatic metalens performance by deriving mathematical equations that govern the tradeoffs between phase dispersion and achievable lens parameters,including the lens diameter,numerical aperture(NA),and bandwidth of achromatic operation.We experimentally demonstrated several dielectric achromatic metalenses reaching the fundamental limitations.These metalenses work in the transmission mode with polarization-independent focusing efficiencies up to 50%and continuously provide a near-constant focal length over λ=1200–1650 nm.These unprecedented properties represent a major advance compared to the state of the art and a major step toward practical implementations of metalenses.展开更多
Optical devices are highly attractive for biosensing as they can not only enable quantitative measurements of analytes but also provide information on molecular structures.Unfortunately,typical refractive index-based ...Optical devices are highly attractive for biosensing as they can not only enable quantitative measurements of analytes but also provide information on molecular structures.Unfortunately,typical refractive index-based optical sensors do not have sufficient sensitivity to probe the binding of low-molecular-weight analytes.Non-optical devices such as field-effect transistors can be more sensitive but do not offer some of the significant features of optical devices,particularly molecular fingerprinting.We present optical conductivity-based mid-infrared(mid-IR)biosensors that allow for sensitive and quantitative measurements of low-molecular-weight analytes as well as the enhancement of spectral fingerprints.The sensors employ a hybrid metasurface consisting of monolayer graphene and metallic nano-antennas and combine individual advantages of plasmonic,electronic and spectroscopic approaches.First,the hybrid metasurface sensors can optically detect target molecule-induced carrier doping to graphene,allowing highly sensitive detection of low-molecular-weight analytes despite their small sizes.Second,the resonance shifts caused by changes in graphene optical conductivity is a well-defined function of graphene carrier density,thereby allowing for quantification of the binding of molecules.Third,the sensor performance is highly stable and consistent thanks to its insensitivity to graphene carrier mobility degradation.Finally,the sensors can also act as substrates for surfaceenhanced infrared spectroscopy.We demonstrated the measurement of monolayers of sub-nanometer-sized molecules or particles and affinity binding-based quantitative detection of glucose down to 200 pM(36 pg/mL).We also demonstrated enhanced fingerprinting of minute quantities of glucose and polymer molecules.展开更多
Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront.In optical metasurfaces,for example,the localized modes of individual meta-units govern the wavefron...Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront.In optical metasurfaces,for example,the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth,while nonlocal lattice modes extended over many unit cells support high quality-factor resonances.Here,we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light,realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected.Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase.We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces,each supporting multiple independently controlled quasi-bound states in the continuum,molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum.Such a platform is scalable to the visible for applications in augmented reality and transparent displays.展开更多
Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in ...Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in silk cocoon fibers of the comet moth,Argema mittrei.The fibers are populated with a high density of air voids randomly distributed across the fiber cross-section but are invariant along the fiber.These filamentary air voids strongly scatter light in the solar spectrum.A single silk fiber measuring~50μm thick can reflect 66%of incoming solar radiation,and this,together with the fibers’high emissivity of 0.88 in the mid-infrared range,allows the cocoon to act as an efficient radiative-cooling device.Drawing inspiration from these natural radiative-cooling fibers,biomimetic nanostructured fibers based on both regenerated silk fibroin and polyvinylidene difluoride are fabricated through wet spinning.Optical characterization shows that these fibers exhibit exceptional optical properties for radiative-cooling applications:nanostructured regenerated silk fibers provide a solar reflectivity of 0.73 and a thermal emissivity of 0.90,and nanostructured polyvinylidene difluoride fibers provide a solar reflectivity of 0.93 and a thermal emissivity of 0.91.The filamentary air voids lead to highly directional scattering,giving the fibers a highly reflective sheen,but more interestingly,they enable guided optical modes to propagate along the fibers through transverse Anderson localization.This discovery opens up the possibility of using wild silkmoth fibers as a biocompatible and bioresorbable material for optical signal and image transport.展开更多
基金We thank Shiyue Liu from School of Life Sciences in The Chinese University of Hong Kong for helpful discussions.This work is supported under the PROCORE-France/Hong Kong Joint Research Scheme(F-CUHK402/19)the Research Grants Council,Hong Kong Special Administration Region(AoE/P-02/12,14210517,14207419,N_CUHK407/16)the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No.798916.Y.Wang is supported under the Hong Kong PhD Fellowship Scheme.
文摘Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer,monitoring treatment and detecting relapse.Here,a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial.By precisely engineering the configuration with atomically thin materials,the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect.Based on our knowledge,it is the first experimental demonstration of a lateral position signal change>340μm at a sensing interface from all optical techniques.With this enhanced plasmonic effect,the detection limit has been experimentally demonstrated to be 10^(-15) mol L^(−1) for TNF-α cancer marker,which has been found in various human diseases including inflammatory diseases and different kinds of cancer.The as-reported novel integration of atomically thin Ge_(2)Sb_(2)Te_(5) with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.
基金supported by the Defense Advanced Research Projects Agency(grant no.D15AP00111 and HR0011-17-2-0017)the National Science Foundation(grant no.ECCS-1307948 and QII-TAQS-1936359)+2 种基金the Air Force Office of Scientific Research(grant no.FA9550-14-1-0389 and FA9550-16-1-0322)support from the NSF IGERT program(grant no.DGE-1069240)supported by the US Department of Energy,Office of Basic Energy Sciences(contract no.DESC0012704).
文摘Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in practice,that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies.This opens up applications in computer-generated holography,allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography.We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two-and three-dimensional holographic objects.We show that phaseamplitude metasurfaces enable a few features not attainable in phase-only holography;these include creating artifactfree two-dimensional holographic images,encoding phase and amplitude profiles separately at the object plane,encoding intensity profiles at the metasurface and object planes separately,and controlling the surface textures of three-dimensional holographic objects.
基金supported by the Defense Advanced Research Projects Agency(no.D15AP00111 and no.HR0011-17-2-0017)the Air Force Office of Scientific Research(no.FA9550-14-1-0389 and no.FA9550-16-1-0322)+2 种基金the National Science Foundation(no.ECCS-1307948)support from the NSF IGERT program(no.DGE-1069240)supported by the US Department of Energy,Office of Basic Energy Sciences(contract no.DE-SC0012704)。
文摘Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging systems and to realize new imaging modalities.However,it is a major challenge to create achromatic metalenses that produce a single focal length over a broad wavelength range because of the difficulty in simultaneously engineering phase profiles at distinct wavelengths on a single metasurface.For practical applications,there is a further challenge to create broadband achromatic metalenses that work in the transmission mode for incident light waves with any arbitrary polarization state.We developed a design methodology and created libraries of meta-units—building blocks of metasurfaces—with complex cross-sectional geometries to provide diverse phase dispersions(phase as a function of wavelength),which is crucial for creating broadband achromatic metalenses.We elucidated the fundamental limitations of achromatic metalens performance by deriving mathematical equations that govern the tradeoffs between phase dispersion and achievable lens parameters,including the lens diameter,numerical aperture(NA),and bandwidth of achromatic operation.We experimentally demonstrated several dielectric achromatic metalenses reaching the fundamental limitations.These metalenses work in the transmission mode with polarization-independent focusing efficiencies up to 50%and continuously provide a near-constant focal length over λ=1200–1650 nm.These unprecedented properties represent a major advance compared to the state of the art and a major step toward practical implementations of metalenses.
基金supported by the National Science Foundation(grants no.ECCS-1509760 and ECCS-1307948)a Defense Advanced Research Projects Agency Young Faculty Award(grant no.D15AP00111)+1 种基金the Air Force Office of Scientific Research(grants no.FA9550–14–1–0389 and FA9550–16–1–0322)Research was carried out in part at the Center for Functional Nanomaterials,Brookhaven National Laboratory,which is supported by the US Department of Energy,Office of Basic Energy Sciences(contract no.DE-SC0012704).
文摘Optical devices are highly attractive for biosensing as they can not only enable quantitative measurements of analytes but also provide information on molecular structures.Unfortunately,typical refractive index-based optical sensors do not have sufficient sensitivity to probe the binding of low-molecular-weight analytes.Non-optical devices such as field-effect transistors can be more sensitive but do not offer some of the significant features of optical devices,particularly molecular fingerprinting.We present optical conductivity-based mid-infrared(mid-IR)biosensors that allow for sensitive and quantitative measurements of low-molecular-weight analytes as well as the enhancement of spectral fingerprints.The sensors employ a hybrid metasurface consisting of monolayer graphene and metallic nano-antennas and combine individual advantages of plasmonic,electronic and spectroscopic approaches.First,the hybrid metasurface sensors can optically detect target molecule-induced carrier doping to graphene,allowing highly sensitive detection of low-molecular-weight analytes despite their small sizes.Second,the resonance shifts caused by changes in graphene optical conductivity is a well-defined function of graphene carrier density,thereby allowing for quantification of the binding of molecules.Third,the sensor performance is highly stable and consistent thanks to its insensitivity to graphene carrier mobility degradation.Finally,the sensors can also act as substrates for surfaceenhanced infrared spectroscopy.We demonstrated the measurement of monolayers of sub-nanometer-sized molecules or particles and affinity binding-based quantitative detection of glucose down to 200 pM(36 pg/mL).We also demonstrated enhanced fingerprinting of minute quantities of glucose and polymer molecules.
基金supported by the Nationall Science Foundation(grant no.QI-TAQ5-1936359 and no.ECCS-2004685)and the Air Force fice of Scientifc Research(grant no.FA9550-14-1-0389 and no,FA9550-16-03221.S.C.M.acknowledges support from the NSF Graduate Research Fellowship Program(grant no.DGE-1644869).ACO.acknowledges support from the NSF IGERT program(grant no.DGE-1069240).Device fabrication was carried out at the Columbia Nano lnitiative dleanoom,and at the Advanced Science Research Center NanoFabrication Facility at the Gradute Center of the City University of New York.
文摘Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront.In optical metasurfaces,for example,the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth,while nonlocal lattice modes extended over many unit cells support high quality-factor resonances.Here,we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light,realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected.Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase.We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces,each supporting multiple independently controlled quasi-bound states in the continuum,molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum.Such a platform is scalable to the visible for applications in augmented reality and transparent displays.
基金supported by the NSF(grant no.PHY-1411445)the Air Force Office of Scientific Research(grant nos.FA9550-14-1-0389 and FA9550-16-1-0322)supported by the US Department of Energy,Office of Basic Energy Sciences,under contract no.DE-SC0012704.
文摘Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in silk cocoon fibers of the comet moth,Argema mittrei.The fibers are populated with a high density of air voids randomly distributed across the fiber cross-section but are invariant along the fiber.These filamentary air voids strongly scatter light in the solar spectrum.A single silk fiber measuring~50μm thick can reflect 66%of incoming solar radiation,and this,together with the fibers’high emissivity of 0.88 in the mid-infrared range,allows the cocoon to act as an efficient radiative-cooling device.Drawing inspiration from these natural radiative-cooling fibers,biomimetic nanostructured fibers based on both regenerated silk fibroin and polyvinylidene difluoride are fabricated through wet spinning.Optical characterization shows that these fibers exhibit exceptional optical properties for radiative-cooling applications:nanostructured regenerated silk fibers provide a solar reflectivity of 0.73 and a thermal emissivity of 0.90,and nanostructured polyvinylidene difluoride fibers provide a solar reflectivity of 0.93 and a thermal emissivity of 0.91.The filamentary air voids lead to highly directional scattering,giving the fibers a highly reflective sheen,but more interestingly,they enable guided optical modes to propagate along the fibers through transverse Anderson localization.This discovery opens up the possibility of using wild silkmoth fibers as a biocompatible and bioresorbable material for optical signal and image transport.