Three-dimensional(3D)graphene monoliths are a new carbon material,that has tremendous potential in the fields of energy conversion and storage.They can solve the limitations of two-dimensional(2D)graphene sheets,inclu...Three-dimensional(3D)graphene monoliths are a new carbon material,that has tremendous potential in the fields of energy conversion and storage.They can solve the limitations of two-dimensional(2D)graphene sheets,including interlayer restacking,high contact resistance,and insufficient pore accessibility.By constructing interconnected porous networks,3D graphenes not only retain the intrinsic advantages of 2D graphene sheets,such as high specific surface area,excellent electrical and thermal conductivities,good mechanical properties,and outstanding chemical stability,but also enable efficient mass transport of external fluid species.We summarize the fabrication methods for 3D graphenes,with a particular focus on their applications in energy-related systems.Techniques including chemical reduction assembly,chemical vapor deposition,3D printing,chemical blowing,and zinc-tiered pyrolysis have been developed to change their pore structure and elemental composition,and ways in which they can be integrated with functional components.In terms of energy conversion and storage,they have found broad use in buffering mechanical impacts,suppressing noise,photothermal conversion,electromagnetic shielding and absorption.They have also been used in electrochemical energy systems such as supercapacitors,secondary batteries,and electrocatalysis.By reviewing recent progress in structural design and new applications,we also discuss the problems these materials face,including scalable fabrication and precise pore structure control,and possible new applications.展开更多
The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex...The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.展开更多
Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based ...Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based mechanical beam deflectors confront a huge challenge due to their large sizes and incompatibility to the device integration.Here we propose an all-dielectric flat metasurface beam deflector which is composed of a single layer array of TiO_2 nanoantennas resting on a fused-silica substrate.Numerical simulations are performed to demonstrate that the proposed deflectors are able to efficiently deflect the incident beam for different angles with transmission efficiency higher than 80%at visible frequencies.This ultrathin all-dielectric metasurface deflector may have great potential applications in integrated optics.展开更多
Perception of color with our eyes is one of the major sources of information that we gain from our surround-ings.The color of an object depends on which portion of light(range of wavelengths)reaches our eyes.In nature...Perception of color with our eyes is one of the major sources of information that we gain from our surround-ings.The color of an object depends on which portion of light(range of wavelengths)reaches our eyes.In nature,struc-tura1 colors are often caused by the interaction of light with dielectric structures whose dim ensions are on the order of visible-light wavelengths.For example,in beetles,the color is originated from the microstructure of the skin which is acting as scattering center;while in some butterflies,the colorful patterns are routed from the reflection from the top of the wings.Different optical interactions,including multilayer interference,light scattering and photonic crystal eflfect,give rise to selective transmission or reflection of particular light wavelengths.which leads to the generation of structural colors.W ith the consumption of dyes and pigments,recycling of colored discarded m aterials has been a very difficult issue because of the hardships in relation to the dissociation of diverse chemica1 compounds present in the colorant agents.Plasmonic colors therefore draw attention as they enable generation of vivid colors only by geometrical arrange-ment of m etals which not only eases the recycling but also enhances the chemical stability of the colors.Plasm onic colors are structural colors that originate from the interaction between light and metallic nanostructures.Rapid development in nanofabrication and characterization of plasmonic structures provides an efficient way to control light properties at subwavelength scale,which can generate plasmonic structural colors.The engineering of plasmonic colors is a promising rapidly em erging research field that could have a large technological impact.Artiflcia1 surfaces,in particular,on which the colors are generated via a resonant interaction between light and subwavelength metallic nanostructures,have emerged as nanomaterials or metam aterials for the realization of structura1 colors.Here we introduce several representa-tive plasmonic nanostructures which can generate visible structural colors,including nanogratings,perforated metallic film s,metal-insulator-meta1 resonators,dynamically tunable color generators and perfect absorbers.w e highlight the properties of plasmonic colors and discuss the intrinsic plasmonic resonance m echanism s.Plasmonic structural colors have features of sub-diffraction localization,high-fidelity color rendering and rapid responses of external changes,which are believed to offer a promising future in the applications including ultra-high resolution color displaB spectral filtering and sensing,holography,three-dimensiona1 stereoscopic imaging and real-time colors controlling with extremely com-pact device architectures.展开更多
基金supported by National Natural Science Foundation of China(52272039,U23B2075,51972168)Key Research and Development Program in Jiangsu Province(BE2023085)Natural Science Foundation of Jiangsu Province of China(BK20231406)。
文摘Three-dimensional(3D)graphene monoliths are a new carbon material,that has tremendous potential in the fields of energy conversion and storage.They can solve the limitations of two-dimensional(2D)graphene sheets,including interlayer restacking,high contact resistance,and insufficient pore accessibility.By constructing interconnected porous networks,3D graphenes not only retain the intrinsic advantages of 2D graphene sheets,such as high specific surface area,excellent electrical and thermal conductivities,good mechanical properties,and outstanding chemical stability,but also enable efficient mass transport of external fluid species.We summarize the fabrication methods for 3D graphenes,with a particular focus on their applications in energy-related systems.Techniques including chemical reduction assembly,chemical vapor deposition,3D printing,chemical blowing,and zinc-tiered pyrolysis have been developed to change their pore structure and elemental composition,and ways in which they can be integrated with functional components.In terms of energy conversion and storage,they have found broad use in buffering mechanical impacts,suppressing noise,photothermal conversion,electromagnetic shielding and absorption.They have also been used in electrochemical energy systems such as supercapacitors,secondary batteries,and electrocatalysis.By reviewing recent progress in structural design and new applications,we also discuss the problems these materials face,including scalable fabrication and precise pore structure control,and possible new applications.
基金supported by the National Nat-ural Science Foundation of China(Nos.12192251,12174185,92163216,and 62288101).
文摘The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.
基金supported in part by the National Natural Science Foundation of China under Grant (61575092)support from the Thousand Talents Program for Young Professionals,Collaborative Innovations Center of Advanced Microstructures
文摘Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based mechanical beam deflectors confront a huge challenge due to their large sizes and incompatibility to the device integration.Here we propose an all-dielectric flat metasurface beam deflector which is composed of a single layer array of TiO_2 nanoantennas resting on a fused-silica substrate.Numerical simulations are performed to demonstrate that the proposed deflectors are able to efficiently deflect the incident beam for different angles with transmission efficiency higher than 80%at visible frequencies.This ultrathin all-dielectric metasurface deflector may have great potential applications in integrated optics.
文摘Perception of color with our eyes is one of the major sources of information that we gain from our surround-ings.The color of an object depends on which portion of light(range of wavelengths)reaches our eyes.In nature,struc-tura1 colors are often caused by the interaction of light with dielectric structures whose dim ensions are on the order of visible-light wavelengths.For example,in beetles,the color is originated from the microstructure of the skin which is acting as scattering center;while in some butterflies,the colorful patterns are routed from the reflection from the top of the wings.Different optical interactions,including multilayer interference,light scattering and photonic crystal eflfect,give rise to selective transmission or reflection of particular light wavelengths.which leads to the generation of structural colors.W ith the consumption of dyes and pigments,recycling of colored discarded m aterials has been a very difficult issue because of the hardships in relation to the dissociation of diverse chemica1 compounds present in the colorant agents.Plasmonic colors therefore draw attention as they enable generation of vivid colors only by geometrical arrange-ment of m etals which not only eases the recycling but also enhances the chemical stability of the colors.Plasm onic colors are structural colors that originate from the interaction between light and metallic nanostructures.Rapid development in nanofabrication and characterization of plasmonic structures provides an efficient way to control light properties at subwavelength scale,which can generate plasmonic structural colors.The engineering of plasmonic colors is a promising rapidly em erging research field that could have a large technological impact.Artiflcia1 surfaces,in particular,on which the colors are generated via a resonant interaction between light and subwavelength metallic nanostructures,have emerged as nanomaterials or metam aterials for the realization of structura1 colors.Here we introduce several representa-tive plasmonic nanostructures which can generate visible structural colors,including nanogratings,perforated metallic film s,metal-insulator-meta1 resonators,dynamically tunable color generators and perfect absorbers.w e highlight the properties of plasmonic colors and discuss the intrinsic plasmonic resonance m echanism s.Plasmonic structural colors have features of sub-diffraction localization,high-fidelity color rendering and rapid responses of external changes,which are believed to offer a promising future in the applications including ultra-high resolution color displaB spectral filtering and sensing,holography,three-dimensiona1 stereoscopic imaging and real-time colors controlling with extremely com-pact device architectures.
