Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are des...Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture （NA） focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld （RS） diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.展开更多
Photonic synapses combining photosensitivity and synaptic function can efficiently perceive and memorize visual information,making them crucial for the development of artificial vision systems.However,the development ...Photonic synapses combining photosensitivity and synaptic function can efficiently perceive and memorize visual information,making them crucial for the development of artificial vision systems.However,the development of high-performance photonic synapses with low power consumption and rapid optical erasing ability remains challenging.Here,we propose a photon-modulated charging/discharging mechanism for self-powered photonic synapses.The current hysteresis enables the devices based on CsPbBr3/solvent/carbon nitride multilayer architecture to emulate synaptic behaviors,such as excitatory postsynaptic currents,paired-pulse facilitation,and long/short-term memory.Intriguingly,the unique radiation direction-dependent photocurrent endows the photonic synapses with the capability of optical writing and rapid optical erasing.Moreover,the photonic synapses exhibit exceptional performance in contrast enhancement and noise reduction owing to the notable synaptic plasticity.In simulations based on artificial neural network(ANN)algorithms,the pre-processing by our photonic synapses improves the recognition rate of handwritten digit from 11.4%(200 training epochs)to 85%(~60 training epochs).Furthermore,due to the excellent feature extraction and memory capability,an array based on the photonic synapses can imitate facial recognition of human retina without the assistance of ANN.展开更多
The ever-increasing demand for data capacity and information processing speed is driving the development of new techniques to break the performance limitations of current electronic-based data processing systems.Photo...The ever-increasing demand for data capacity and information processing speed is driving the development of new techniques to break the performance limitations of current electronic-based data processing systems.Photonic integrated circuits(PICs)have been promising candidates for nextgeneration chip technology,featuring broad bandwidth,low power consumption,and ultrafast data processing speed.Recent advances in three-dimensional(3D)PIC fabrication and integration of two-dimensional(2D)materials with unique structures and distinctive properties have accelerated PIC development,yielding new possibilities for device realization with outstanding performance and new features.Advanced nanofabrication techniques are fundamentally important for device realization,among which laser nanofabrication,exhibiting one-step and maskless writing capability,has been widely used to fabricate 2D/3D PICs.Although there are several reviews about the fabrication of 2D or 3D PICs,none of them touched on the potential of integrating 2D materials with 3D PICs,which opens new avenues for integration and functionalities and will be substantially important for future development.This review provides a comprehensive overview of laser nanofabrication techniques in multidimensional structure manufacturing for PIC applications.Building on the recent advancements in 3D PIC fabrication and 2D-material-based functional devices,we highlight the potential of integrating 2D materials with 3D PICs.This integration paves the way for creating multidimensional structures with unprecedented optical properties and functionalities,unlocking opportunities that have yet to be explored.By highlighting these possibilities,this review aims to foster new insights and inspire novel directions in the field of PICs.展开更多
Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due...Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due to their high refractive indices.However,achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency.Here we report a universal method to transform 2D monolayers into ultrathin flat lenses.Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer,which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials.We achieved highly efficient 3D focusing with subwavelength resolution and diffractionlimited imaging.The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications.Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.展开更多
Particle nanotracking(PNT)is highly desirable in lab-on-a-chip systems for flexible and convenient multiparameter measurement.An ultrathin flat lens is the preferred imaging device in such a system,with the advantage ...Particle nanotracking(PNT)is highly desirable in lab-on-a-chip systems for flexible and convenient multiparameter measurement.An ultrathin flat lens is the preferred imaging device in such a system,with the advantage of high focusing performance and compactness.However,PNT using ultrathin flat lenses has not been demonstrated so far because PNT requires the clear knowledge of the relationship between the object and image in the imaging system.Such a relationship still remains elusive in ultrathin flat lens-based imaging systems because they operate based on diffraction rather than refraction.In this paper,we experimentally reveal the imaging relationship of a graphene metalens using nanohole arrays with micrometer spacing.The distance relationship between the object and image as well as the magnification ratio is acquired with nanometer accuracy.The measured imaging relationship agrees well with the theoretical prediction and is expected to be applicable to other ultrathin flat lenses based on the diffraction principle.By analyzing the high-resolution images from the graphene metalens using the imaging relationship,3D trajectories of particles with high position accuracy in PNT have been achieved.The revealed imaging relationship for metalenses is essential in designing different types of integrated optical systems,including digital cameras,microfluidic devices,virtual reality devices,telescopes,and eyeglasses,and thus will find broad applications.展开更多
Flat lenses thinner than a wavelength promise to replace conventional refractive lenses in miniaturized optical systems.However,Fresnel zone plate flat lens designs require dense annuli,which significantly challenges ...Flat lenses thinner than a wavelength promise to replace conventional refractive lenses in miniaturized optical systems.However,Fresnel zone plate flat lens designs require dense annuli,which significantly challenges nanofabrication resolution.Herein,we propose a new implementation of detour phase graphene flat lens with flexible annular number and width.Several graphene metalenses demonstrated that with a flexible selection of the line density and width,the metalenses can achieve the same focal length without significant distortions.This will significantly weaken the requirement of the nanofabrication system which is important for the development of large-scale flat lenses in industry applications.展开更多
Optical beams carrying orbital angular momentum(OAM)play an important role in micro-/nanoparticle manipulation and information multiplexing in optical communications.Conventional OAM generation setups require bulky op...Optical beams carrying orbital angular momentum(OAM)play an important role in micro-/nanoparticle manipulation and information multiplexing in optical communications.Conventional OAM generation setups require bulky optical elements and are unsuitable for on-chip integration.OAM generators based on metasurfaces can achieve ultracompact designs.However,they generally have limited working bandwidth and require complex designs and multistep time-consuming fabrication processes.In comparison,graphene metalenses based on the diffraction principle have simple designs and can be fabricated by laser nanoprinting in a single step.Here,we demonstrate that a single ultrathin(200 nm)graphene OAM metalens can integrate OAM generation and high-resolution focusing functions in a broad bandwidth,covering the entire visible wavelength region.Broadband graphene OAM metalenses with flexibly controlled topological charges are analytically designed using the detour phase method considering the dispersionless feature of the graphene material and fabricated using ultrafast laser nanoprinting.The experimental results agree well with the theoretical predictions,which demonstrate the accuracy of the design method.The broadband graphene OAM metalenses can find broad applications in miniaturized and integrated photonic devices enabled by OAM beams.展开更多
Light beams carrying orbital angular momentum(OAM)have inspired various advanced applications,and such abundant practical applications in turn demand complex generation and manipulation of optical vortices.Here,we pro...Light beams carrying orbital angular momentum(OAM)have inspired various advanced applications,and such abundant practical applications in turn demand complex generation and manipulation of optical vortices.Here,we propose a multifocal graphene vortex generator,which can produce broadband angular momentum cascade containing continuous integer non-diffracting vortex modes.Our device naturally embodies a continuous spiral slit vortex generator and a zone plate,which enables the generation of high-quality continuous vortex modes with deep depths of foci.Meanwhile,the generated vortex modes can be simultaneously tuned through incident wavelength and position of the focal plane.The elegant structure of the device largely improves the design efficiency and can be fabricated by laser nanofabrication in a single step.Moreover,the outstanding property of graphene may enable new possibilities in enormous practical applications,even in some harsh environments,such as aerospace.展开更多
The realization of a high numerical aperture(NA) fiber lens is critical for achieving high imaging resolution in endoscopes, enabling subwavelength operation in optical tweezers and high efficiency coupling between op...The realization of a high numerical aperture(NA) fiber lens is critical for achieving high imaging resolution in endoscopes, enabling subwavelength operation in optical tweezers and high efficiency coupling between optical fibers and photonic chips. However, it remains challenging with conventional design and fabrication. Here we propose an ultrathin(400 nm) graphene oxide(GO) film lens fabricated in situ on a standard single-mode fiber facet using the femtosecond laser direct writing technique. An extremely high NA of 0.89 is achieved with a near diffraction-limited focal spot(FWHM = 0.68λ), which is verified theoretically and experimentally. The diameter of the fabricated fiber GO lens is as small as 12 μm with no beam expansion structure. The proposed fiber GO lens is promising for applications such as super-resolution imaging, compact optical tweezers, medical endoscopes,and on-chip integration.展开更多
Compact micro-spectrometers have gained significant attention due to their ease of integration and real-time spectrum measurement capabilities.However,size reduction often compromises performance,particularly in resol...Compact micro-spectrometers have gained significant attention due to their ease of integration and real-time spectrum measurement capabilities.However,size reduction often compromises performance,particularly in resolution and measurable wavelength range.This work proposes a computational micro-spectrometer based on an ultra-thin(~250 nm)detour-phased graphene oxide planar lens with a sub-millimeter footprint,utilizing a spectral-to-spatial mapping method.The varying intensity pattern along the focal axis of the lens acts as a measurement signal,simplifying the system and enabling real-time spectrum acquisition.Combined with computational retrieval method,an input spectrum is reconstructed with a wavelength interval down to 5 nm,representing a 5-time improvement compared with the result when not using computational method.In an optical compartment of 200μm by 200μm by 450μm from lens profile to the detector surface,the ultracompact spectrometer achieves broad spectrum measurement covering the visible range(420−750 nm)with a wavelength interval of 15 nm.Our compact computational micro-spectrometer paves the way for integration into portable,handheld,and wearable devices,holding promise for diverse real-time applications like in-situ health monitoring(e.g.,tracking blood glucose levels),food quality assessment,and portable counterfeit detection.展开更多
文摘Graphene oxide （GO） ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture （NA） focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld （RS） diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.
基金supported by the Natural Science Foundation of Shandong Province(ZR2021YQ32)the China Postdoctoral Science Foundation(2023M740472)+2 种基金the National Natural Science Foundation of China(62175162,62205214,and 61901222)the Taishan Scholars Program of Shandong Province(tsqn201909117)the Special Fund for Science and Technology Innovation Teams of Shanxi Province and Foundation of Shenzhen Science and Technology(20200814100534001).
文摘Photonic synapses combining photosensitivity and synaptic function can efficiently perceive and memorize visual information,making them crucial for the development of artificial vision systems.However,the development of high-performance photonic synapses with low power consumption and rapid optical erasing ability remains challenging.Here,we propose a photon-modulated charging/discharging mechanism for self-powered photonic synapses.The current hysteresis enables the devices based on CsPbBr3/solvent/carbon nitride multilayer architecture to emulate synaptic behaviors,such as excitatory postsynaptic currents,paired-pulse facilitation,and long/short-term memory.Intriguingly,the unique radiation direction-dependent photocurrent endows the photonic synapses with the capability of optical writing and rapid optical erasing.Moreover,the photonic synapses exhibit exceptional performance in contrast enhancement and noise reduction owing to the notable synaptic plasticity.In simulations based on artificial neural network(ANN)algorithms,the pre-processing by our photonic synapses improves the recognition rate of handwritten digit from 11.4%(200 training epochs)to 85%(~60 training epochs).Furthermore,due to the excellent feature extraction and memory capability,an array based on the photonic synapses can imitate facial recognition of human retina without the assistance of ANN.
基金support through the Industrial Transformation Training Centres Scheme(No.IC180100005)the Australia Research Council through Future Fellowship Scheme(No.FT210100806)+10 种基金the Discovery Project Scheme(Nos.DP190103186,DP220100603,and DP250100980)the Linkage Project Scheme(No.LP210100467)the Industrial Transformation Research Hubs Scheme(No.IH240100009)the Centre of Excellence Program(No.CE230100006)support through the Future Fellowship Scheme(No.FT220100559)the Linkage Project Scheme(No.LP240100504)support through the Key Research and Development Program of Shandong Province(No.2024ZLGX02-3)the National Natural Science Foundation of China(No.12204274)the Natural Science Foundation of Shandong Province(No.ZR2022QA033)support through the National Natural Science Foundation of China(Nos.12361141815 and 12174222)the Taishan Scholar Foundation of Shandong Province(No.tspd20210303).
文摘The ever-increasing demand for data capacity and information processing speed is driving the development of new techniques to break the performance limitations of current electronic-based data processing systems.Photonic integrated circuits(PICs)have been promising candidates for nextgeneration chip technology,featuring broad bandwidth,low power consumption,and ultrafast data processing speed.Recent advances in three-dimensional(3D)PIC fabrication and integration of two-dimensional(2D)materials with unique structures and distinctive properties have accelerated PIC development,yielding new possibilities for device realization with outstanding performance and new features.Advanced nanofabrication techniques are fundamentally important for device realization,among which laser nanofabrication,exhibiting one-step and maskless writing capability,has been widely used to fabricate 2D/3D PICs.Although there are several reviews about the fabrication of 2D or 3D PICs,none of them touched on the potential of integrating 2D materials with 3D PICs,which opens new avenues for integration and functionalities and will be substantially important for future development.This review provides a comprehensive overview of laser nanofabrication techniques in multidimensional structure manufacturing for PIC applications.Building on the recent advancements in 3D PIC fabrication and 2D-material-based functional devices,we highlight the potential of integrating 2D materials with 3D PICs.This integration paves the way for creating multidimensional structures with unprecedented optical properties and functionalities,unlocking opportunities that have yet to be explored.By highlighting these possibilities,this review aims to foster new insights and inspire novel directions in the field of PICs.
基金support from the Australian Research Council through the Discovery Project scheme(DP190103186)the Industrial Transformation Training Centres scheme(Grant No.IC180100005)+6 种基金support from the Australian Postgraduate Award(APA)and international postgraduate research scholarship(IPRS)support from the National Key Research&Development Program(No.2016YFA0201902)aShenzhen Nanshan District Pilotage Team Program(LHTD20170006)support from the Australian Research Council(FT150100450 and CE170100039)financial support from the A*STAR Pharos Program(grant number 1527000014,with project number R-263-000-B91-305)the National Research Foundation,Prime Minister’s Office,Singapore under its Competitive Research Program(CRP award NRF CRP22-2019-0006)the support of the National Research Foundation-Competitive Research Program(NRF-CRP21–2018–007).
文摘Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due to their high refractive indices.However,achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency.Here we report a universal method to transform 2D monolayers into ultrathin flat lenses.Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer,which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials.We achieved highly efficient 3D focusing with subwavelength resolution and diffractionlimited imaging.The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications.Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.
基金Australian Research Council(DP190103186,IC180100005)China Scholarship Council(201706030189).
文摘Particle nanotracking(PNT)is highly desirable in lab-on-a-chip systems for flexible and convenient multiparameter measurement.An ultrathin flat lens is the preferred imaging device in such a system,with the advantage of high focusing performance and compactness.However,PNT using ultrathin flat lenses has not been demonstrated so far because PNT requires the clear knowledge of the relationship between the object and image in the imaging system.Such a relationship still remains elusive in ultrathin flat lens-based imaging systems because they operate based on diffraction rather than refraction.In this paper,we experimentally reveal the imaging relationship of a graphene metalens using nanohole arrays with micrometer spacing.The distance relationship between the object and image as well as the magnification ratio is acquired with nanometer accuracy.The measured imaging relationship agrees well with the theoretical prediction and is expected to be applicable to other ultrathin flat lenses based on the diffraction principle.By analyzing the high-resolution images from the graphene metalens using the imaging relationship,3D trajectories of particles with high position accuracy in PNT have been achieved.The revealed imaging relationship for metalenses is essential in designing different types of integrated optical systems,including digital cameras,microfluidic devices,virtual reality devices,telescopes,and eyeglasses,and thus will find broad applications.
基金Natural Science Foundation of Guangdong Province(2016A030310130)Australia Research Council(the Discovery Project scheme)(DP190103186)+5 种基金Australian Research Council Industrial Transformation Training Centre for Functional Grains(IC180100005)National Natural Science Foundation of China(62175162)Foundation of Shenzhen Science and Technology(20200814100534001)Science,Technology and Innovation Commission of Shenzhen Municipality(KQTD20170330110444030,KQTD20180412181324255)Foundation of Guangdong Education Committee(2020KTSCX117)China Postdoctoral Science Foundation(2021M692173)。
文摘Flat lenses thinner than a wavelength promise to replace conventional refractive lenses in miniaturized optical systems.However,Fresnel zone plate flat lens designs require dense annuli,which significantly challenges nanofabrication resolution.Herein,we propose a new implementation of detour phase graphene flat lens with flexible annular number and width.Several graphene metalenses demonstrated that with a flexible selection of the line density and width,the metalenses can achieve the same focal length without significant distortions.This will significantly weaken the requirement of the nanofabrication system which is important for the development of large-scale flat lenses in industry applications.
基金the Australia Research Council(grant no.DP220100603,FT210100806,and FT220100559)the Industrial Transformation Training Centres scheme(grant no.IC180100005)Linkage Project scheme(LP210200345).
文摘Optical beams carrying orbital angular momentum(OAM)play an important role in micro-/nanoparticle manipulation and information multiplexing in optical communications.Conventional OAM generation setups require bulky optical elements and are unsuitable for on-chip integration.OAM generators based on metasurfaces can achieve ultracompact designs.However,they generally have limited working bandwidth and require complex designs and multistep time-consuming fabrication processes.In comparison,graphene metalenses based on the diffraction principle have simple designs and can be fabricated by laser nanoprinting in a single step.Here,we demonstrate that a single ultrathin(200 nm)graphene OAM metalens can integrate OAM generation and high-resolution focusing functions in a broad bandwidth,covering the entire visible wavelength region.Broadband graphene OAM metalenses with flexibly controlled topological charges are analytically designed using the detour phase method considering the dispersionless feature of the graphene material and fabricated using ultrafast laser nanoprinting.The experimental results agree well with the theoretical predictions,which demonstrate the accuracy of the design method.The broadband graphene OAM metalenses can find broad applications in miniaturized and integrated photonic devices enabled by OAM beams.
基金the support from Advanced Research and Technology Innovation Centre(ARTIC)in National University of Singapore(R-261-518-004-720|A-0005947-1600)the Australia Research Council through the Discovery Project Scheme(DP190103186,DP220100603,and FT210100806)the Industrial Transformation Training Centre Scheme(IC180100005).
文摘Light beams carrying orbital angular momentum(OAM)have inspired various advanced applications,and such abundant practical applications in turn demand complex generation and manipulation of optical vortices.Here,we propose a multifocal graphene vortex generator,which can produce broadband angular momentum cascade containing continuous integer non-diffracting vortex modes.Our device naturally embodies a continuous spiral slit vortex generator and a zone plate,which enables the generation of high-quality continuous vortex modes with deep depths of foci.Meanwhile,the generated vortex modes can be simultaneously tuned through incident wavelength and position of the focal plane.The elegant structure of the device largely improves the design efficiency and can be fabricated by laser nanofabrication in a single step.Moreover,the outstanding property of graphene may enable new possibilities in enormous practical applications,even in some harsh environments,such as aerospace.
基金National Natural Science Foundation of China(62275150)。
文摘The realization of a high numerical aperture(NA) fiber lens is critical for achieving high imaging resolution in endoscopes, enabling subwavelength operation in optical tweezers and high efficiency coupling between optical fibers and photonic chips. However, it remains challenging with conventional design and fabrication. Here we propose an ultrathin(400 nm) graphene oxide(GO) film lens fabricated in situ on a standard single-mode fiber facet using the femtosecond laser direct writing technique. An extremely high NA of 0.89 is achieved with a near diffraction-limited focal spot(FWHM = 0.68λ), which is verified theoretically and experimentally. The diameter of the fabricated fiber GO lens is as small as 12 μm with no beam expansion structure. The proposed fiber GO lens is promising for applications such as super-resolution imaging, compact optical tweezers, medical endoscopes,and on-chip integration.
基金funded by National Key Research and Development Program of China(2022YFF0712500,2022YFC3401100)Guangdong Major Project of Basic and Applied Basic Research No.2020B0301030009+4 种基金the National Natural Science Foundation of China(12004012,92150301,91750203,12041602,91850111,and 12004013)the China Postdoctoral Science Foundation(2020M680230,2020M680220)The author would like to thank the High-performance Computing Platform of Peking UniversityThis work was also supported by Australia Research Council(Grant No.DP220100603,FT210100806,FT220100559)Industrial Transformation Training Centres scheme(Grant No.IC180100005),Linkage Project scheme(LP210200345).
文摘Compact micro-spectrometers have gained significant attention due to their ease of integration and real-time spectrum measurement capabilities.However,size reduction often compromises performance,particularly in resolution and measurable wavelength range.This work proposes a computational micro-spectrometer based on an ultra-thin(~250 nm)detour-phased graphene oxide planar lens with a sub-millimeter footprint,utilizing a spectral-to-spatial mapping method.The varying intensity pattern along the focal axis of the lens acts as a measurement signal,simplifying the system and enabling real-time spectrum acquisition.Combined with computational retrieval method,an input spectrum is reconstructed with a wavelength interval down to 5 nm,representing a 5-time improvement compared with the result when not using computational method.In an optical compartment of 200μm by 200μm by 450μm from lens profile to the detector surface,the ultracompact spectrometer achieves broad spectrum measurement covering the visible range(420−750 nm)with a wavelength interval of 15 nm.Our compact computational micro-spectrometer paves the way for integration into portable,handheld,and wearable devices,holding promise for diverse real-time applications like in-situ health monitoring(e.g.,tracking blood glucose levels),food quality assessment,and portable counterfeit detection.
