With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G)...With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.展开更多
Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms...Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms.Photonic accelerators are designed to accelerate specific categories of computing in the optical domain,especially matrix multiplication,to address the growing demand for computing resources and capacity.Photonic matrix multiplication has much potential to expand the domain of telecommunication,and artificial intelligence benefiting from its superior performance.Recent research in photonic matrix multiplication has flourished and may provide opportunities to develop applications that are unachievable at present by conventional electronic processors.In this review,we first introduce the methods of photonic matrix multiplication,mainly including the plane light conversion method,Mach–Zehnder interferometer method and wavelength division multiplexing method.We also summarize the developmental milestones of photonic matrix multiplication and the related applications.Then,we review their detailed advances in applications to optical signal processing and artificial neural networks in recent years.Finally,we comment on the challenges and perspectives of photonic matrix multiplication and photonic acceleration.展开更多
Graphene has attracted much attention for the realization of high-speed photodetection for silicon photonics over a wide wavelength range.However,the reported fast graphene photodetectors mainly operate in the 1.55μm...Graphene has attracted much attention for the realization of high-speed photodetection for silicon photonics over a wide wavelength range.However,the reported fast graphene photodetectors mainly operate in the 1.55μm wavelength band.In this work,we propose and realize high-performance waveguide photodetectors based on bolometric/photoconductive effects by introducing an ultrathin wide silicon−graphene hybrid plasmonic waveguide,which enables efficient light absorption in graphene at 1.55μm and beyond.When operating at 2μm,the present photodetector has a responsivity of ~70 mA/W and a setup-limited 3 dB bandwidth of >20 GHz.When operating at 1.55μm,the present photodetector also works very well with a broad 3 dB bandwidth of >40 GHz(setup-limited)and a high responsivity of ~0.4 A/W even with a low bias voltage of−0.3 V.This work paves the way for achieving highresponsivity and high-speed silicon-graphene waveguide photodetection in the near/mid-infrared ranges,which has applications in optical communications,nonlinear photonics,and on-chip sensing.展开更多
BACKGROUND： Early recurrence （ER） after hepatic resection （HR） is a poor prognostic factor for patients with hepatocellular carcinoma （HCC）. This study aimed to identify the clinico- pathological features, outc...BACKGROUND： Early recurrence （ER） after hepatic resection （HR） is a poor prognostic factor for patients with hepatocellular carcinoma （HCC）. This study aimed to identify the clinico- pathological features, outcomes, and risk factors for ER after HR for small HCC in order to clarify the reasons why ER is a worse recurrence pattern. METHODS： We retrospectively examined 130 patients who underwent HR for small HCC （___30 mm）. Recurrence was clas- sifted into ER （〈2 years） and late recurrence （LR） （_〉2 years）. The clinicopathological features, outcomes, and risk factors for ER were analyzed by multivariate analysis. RESULTS： ER was observed in 39 patients （30.0%）. The sur- vival rate of the ER group was significantly lower than that of the LR group （P〈0.005）, and ER was an independent prognos- tic factor for poor survival （P=0.0001）. The ER group had a significantly higher frequency （P=0.0039） and shorter interval （P=0.027） of development to carcinoma beyond the Milan criteria （DBMC） compared with the LR group, and ER was an independent risk factor for DBMC （P〈0.0001）. Multi-nodularity, non-simple nodular type, and microvascular invasion were independent predictors for ER （P=0.012, 0.010, and 0.019, respectively）.CONCLUSIONS： ER was a highly malignant recurrence pattern associated with DBMC and subsequent poor survival after HR for small HCC. Multi-nodularity, non-simple nodular type, and microvascular invasion predict ER, and taking these factors into consideration may be useful for the decision of the treatment strategy for small HCC after HR.展开更多
Deep learning in the context of nano-photonics is mostly discussed in terms of its potential for inverse design of photonic devices or nano-structures. Many of the recent works on machine-learning inverse design are h...Deep learning in the context of nano-photonics is mostly discussed in terms of its potential for inverse design of photonic devices or nano-structures. Many of the recent works on machine-learning inverse design are highly specific, and the drawbacks of the respective approaches are often not immediately clear. In this review we want therefore to provide a critical review on the capabilities of deep learning for inverse design and the progress which has been made so far. We classify the different deep-learning-based inverse design approaches at a higher level as well as by the context of their respective applications and critically discuss their strengths and weaknesses. While a significant part of the community’s attention lies on nano-photonic inverse design, deep learning has evolved as a tool for a large variety of applications. The second part of the review will focus therefore on machine learning research in nano-photonics "beyond inverse design." This spans from physics-informed neural networks for tremendous acceleration of photonics simulations, over sparse data reconstruction, imaging and "knowledge discovery" to experimental applications.展开更多
How to explore and exploit the full potential of artificial intelligence(AI)technologies in future wireless communications such as beyond 5G(B5G)and 6G is an extremely hot inter-disciplinary research topic around the ...How to explore and exploit the full potential of artificial intelligence(AI)technologies in future wireless communications such as beyond 5G(B5G)and 6G is an extremely hot inter-disciplinary research topic around the world.On the one hand,AI empowers intelligent resource management for wireless communications through powerful learning and automatic adaptation capabilities.On the other hand,embracing AI in wireless communication resource management calls for new network architecture and system models as well as standardized interfaces/protocols/data formats to facilitate the large-scale deployment of AI in future B5G/6G networks.This paper reviews the state-of-art AI-empowered resource management from the framework perspective down to the methodology perspective,not only considering the radio resource(e.g.,spectrum)management but also other types of resources such as computing and caching.We also discuss the challenges and opportunities for AI-based resource management to widely deploy AI in future wireless communication networks.展开更多
1．前言《变异语用学：聚焦多中心语言的地域变体》（Variational Pragmatics：A Focus on Regional Varieties in Pluricentric Languages）是2008年John Benjamins出版公司出版的Pragmatics ＆ Beyond New
The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectiv...The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity,as well as revolutionary communication and computing paradigms.Among the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces(RISs),which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of functionalities.Incorporating RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one,intended for various networking objectives,such as coverage extension and capacity boosting,spatiotemporal focusing with benefits in energy efficiency and secrecy,and low electromagnetic field exposure.Motivated by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments,in this paper,we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal propagation.We also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems,which constitute a prerequisite step for the optimized incorporation of RISs in future wireless networks.Finally,we discuss the relevance of the RIS technology in the latest wireless communication standards,and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.展开更多
The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical bui...The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.展开更多
Rechargeable batteries of high energy density and overall performance are becoming a critically important technology in the rapidly changing society of the twenty-first century.While lithium-ion batteries have so far ...Rechargeable batteries of high energy density and overall performance are becoming a critically important technology in the rapidly changing society of the twenty-first century.While lithium-ion batteries have so far been the dominant choice,numerous emerging applications call for higher capacity,better safety and lower costs while maintaining sufficient cyclability.The design space for potentially better alternatives is extremely large,with numerous new chemistries and architectures being simultaneously explored.These include other insertion ions(e.g.sodium and numerous multivalent ions),conversion electrode materials(e.g.silicon,metallic anodes,halides and chalcogens)and aqueous and solid electrolytes.However,each of these potential“beyond lithium-ion”alternatives faces numerous challenges that often lead to very poor cyclability,especially at the commercial cell level,while lithium-ion batteries continue to improve in performance and decrease in cost.This review examines fundamental principles to rationalise these numerous developments,and in each case,a brief overview is given on the advantages,advances,remaining challenges preventing cell-level implementation and the state-of-the-art of the solutions to these challenges.Finally,research and development results obtained in academia are compared to emerging commercial examples,as a commentary on the current and near-future viability of these“beyond lithium-ion”alternatives.展开更多
Visible light communication(VLC)has emerged as a promising communication method in 6G.However,the development of receiving devices is much slower than that of transmitting devices,limited by materials,structures,and f...Visible light communication(VLC)has emerged as a promising communication method in 6G.However,the development of receiving devices is much slower than that of transmitting devices,limited by materials,structures,and fabrication.In this paper,we propose and fabricate an InGaN/GaN multiple-quantum-well-based vertical-structure micro-LED-based photodetector(μPD)on a Si substrate.A comprehensive comparison of the photoelectrical performance and communication performance of three sizes ofμPDs,10,50,and 100μm,is presented.The peak responsivity of all threeμPDs is achieved at 400 nm,while the passband full-widths at half maxima are 87,72,and 78 nm for 10,50,and 100μmμPDs,respectively.The−20 dB cutoff bandwidth is up to 822 MHz for 50μmμPD.A data rate of 10.14 Gbps is experimentally demonstrated by bit and power loading discrete multitone modulation and the proposed digital pre-equalizer algorithm over 1 m free space utilizing the self-designed 4×450μmμPD array as a receiver and a 450 nm laser diode as a transmitter.This is the first time a more than 10 Gbps VLC system has been achieved utilizing a GaN-based micro-PD,to the best of our knowledge.The investigation fully demonstrates the superiority of Si substrates and vertical structures in InGaN/GaNμPDs and shows its great potential for high-speed VLC links beyond 10 Gbps.展开更多
基金supported by the National High Technology Research and Development Program of China (863 program) of China under Grant No.2011AA010200 supported by the National Natural Science Foundation of China (NSFC) under Grant No.61771116 and No.91738102
文摘With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
基金Chaoran Huang would like to thank Alexander Tait,Bhavin Shastri and Paul Prucnal for the fruitful discussions.J.J.D.acknowledges the support of the National Key Research and Development Project of China(2018YFB2201901)the National Natural Science Foundation of China(61805090,62075075).
文摘Matrix computation,as a fundamental building block of information processing in science and technology,contributes most of the computational overheads in modern signal processing and artificial intelligence algorithms.Photonic accelerators are designed to accelerate specific categories of computing in the optical domain,especially matrix multiplication,to address the growing demand for computing resources and capacity.Photonic matrix multiplication has much potential to expand the domain of telecommunication,and artificial intelligence benefiting from its superior performance.Recent research in photonic matrix multiplication has flourished and may provide opportunities to develop applications that are unachievable at present by conventional electronic processors.In this review,we first introduce the methods of photonic matrix multiplication,mainly including the plane light conversion method,Mach–Zehnder interferometer method and wavelength division multiplexing method.We also summarize the developmental milestones of photonic matrix multiplication and the related applications.Then,we review their detailed advances in applications to optical signal processing and artificial neural networks in recent years.Finally,we comment on the challenges and perspectives of photonic matrix multiplication and photonic acceleration.
基金supported by the National Major Research and Development Program(No.2018YFB2200200)National Science Fund for Distinguished Young Scholars(61725503)+2 种基金National Natural Science Foundation of China(NSFC)(61905210 and 91950205)China Postdoctoral Science Foundation(2019M662041)Zhejiang Provincial Natural Science Foundation(LZ18F050001 and LD19F050001).
文摘Graphene has attracted much attention for the realization of high-speed photodetection for silicon photonics over a wide wavelength range.However,the reported fast graphene photodetectors mainly operate in the 1.55μm wavelength band.In this work,we propose and realize high-performance waveguide photodetectors based on bolometric/photoconductive effects by introducing an ultrathin wide silicon−graphene hybrid plasmonic waveguide,which enables efficient light absorption in graphene at 1.55μm and beyond.When operating at 2μm,the present photodetector has a responsivity of ~70 mA/W and a setup-limited 3 dB bandwidth of >20 GHz.When operating at 1.55μm,the present photodetector also works very well with a broad 3 dB bandwidth of >40 GHz(setup-limited)and a high responsivity of ~0.4 A/W even with a low bias voltage of−0.3 V.This work paves the way for achieving highresponsivity and high-speed silicon-graphene waveguide photodetection in the near/mid-infrared ranges,which has applications in optical communications,nonlinear photonics,and on-chip sensing.
文摘BACKGROUND： Early recurrence （ER） after hepatic resection （HR） is a poor prognostic factor for patients with hepatocellular carcinoma （HCC）. This study aimed to identify the clinico- pathological features, outcomes, and risk factors for ER after HR for small HCC in order to clarify the reasons why ER is a worse recurrence pattern. METHODS： We retrospectively examined 130 patients who underwent HR for small HCC （___30 mm）. Recurrence was clas- sifted into ER （〈2 years） and late recurrence （LR） （_〉2 years）. The clinicopathological features, outcomes, and risk factors for ER were analyzed by multivariate analysis. RESULTS： ER was observed in 39 patients （30.0%）. The sur- vival rate of the ER group was significantly lower than that of the LR group （P〈0.005）, and ER was an independent prognos- tic factor for poor survival （P=0.0001）. The ER group had a significantly higher frequency （P=0.0039） and shorter interval （P=0.027） of development to carcinoma beyond the Milan criteria （DBMC） compared with the LR group, and ER was an independent risk factor for DBMC （P〈0.0001）. Multi-nodularity, non-simple nodular type, and microvascular invasion were independent predictors for ER （P=0.012, 0.010, and 0.019, respectively）.CONCLUSIONS： ER was a highly malignant recurrence pattern associated with DBMC and subsequent poor survival after HR for small HCC. Multi-nodularity, non-simple nodular type, and microvascular invasion predict ER, and taking these factors into consideration may be useful for the decision of the treatment strategy for small HCC after HR.
基金CALMIP Toulouse(p20010)Engineering and Physical Sciences Research Council(EP/M009122/1)Deutsche Forschungsgemeinschaft(WI 5261/1-1)。
文摘Deep learning in the context of nano-photonics is mostly discussed in terms of its potential for inverse design of photonic devices or nano-structures. Many of the recent works on machine-learning inverse design are highly specific, and the drawbacks of the respective approaches are often not immediately clear. In this review we want therefore to provide a critical review on the capabilities of deep learning for inverse design and the progress which has been made so far. We classify the different deep-learning-based inverse design approaches at a higher level as well as by the context of their respective applications and critically discuss their strengths and weaknesses. While a significant part of the community’s attention lies on nano-photonic inverse design, deep learning has evolved as a tool for a large variety of applications. The second part of the review will focus therefore on machine learning research in nano-photonics "beyond inverse design." This spans from physics-informed neural networks for tremendous acceleration of photonics simulations, over sparse data reconstruction, imaging and "knowledge discovery" to experimental applications.
文摘How to explore and exploit the full potential of artificial intelligence(AI)technologies in future wireless communications such as beyond 5G(B5G)and 6G is an extremely hot inter-disciplinary research topic around the world.On the one hand,AI empowers intelligent resource management for wireless communications through powerful learning and automatic adaptation capabilities.On the other hand,embracing AI in wireless communication resource management calls for new network architecture and system models as well as standardized interfaces/protocols/data formats to facilitate the large-scale deployment of AI in future B5G/6G networks.This paper reviews the state-of-art AI-empowered resource management from the framework perspective down to the methodology perspective,not only considering the radio resource(e.g.,spectrum)management but also other types of resources such as computing and caching.We also discuss the challenges and opportunities for AI-based resource management to widely deploy AI in future wireless communication networks.
文摘1．前言《变异语用学：聚焦多中心语言的地域变体》（Variational Pragmatics：A Focus on Regional Varieties in Pluricentric Languages）是2008年John Benjamins出版公司出版的Pragmatics ＆ Beyond New
基金supported by the EU H2020 Industrial Leadership Project(No.101017011)the Scientific and Technological Research Council of Turkey(TUBITAK)(No.120E401).
文摘The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity,as well as revolutionary communication and computing paradigms.Among the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces(RISs),which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of functionalities.Incorporating RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one,intended for various networking objectives,such as coverage extension and capacity boosting,spatiotemporal focusing with benefits in energy efficiency and secrecy,and low electromagnetic field exposure.Motivated by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments,in this paper,we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal propagation.We also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems,which constitute a prerequisite step for the optimized incorporation of RISs in future wireless networks.Finally,we discuss the relevance of the RIS technology in the latest wireless communication standards,and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.
基金Q.X.acknowledges support from National Natural Science Foundation of China(Grants Nos.62075113,61675114)S.S.is supported by National Key Research and Development Program of China(Nos.2020YFA0710101,2017YFA0303504)+8 种基金National Natural Science Foundation of China(11874118)Natural Science Foundation of Shanghai(18ZR1403400,20JC1414601)Fudan University-CIOMP Joint Fund(No.FC2018-008)M.Z.is supported by National Natural Science Foundation of China(61775069,61635004)J.A.F.is supported by Office of Naval Research(under Award No.N00014-20-1-2105)ARPA-E(under Award No.DE-AR0001212)Z.X.and X.Y.acknowledge support from National Natural Science Foundation of China(61935013,U1701661,61975133)the Natural Science Foundation of Guangdong Province(2020A1515011185)the Science and Technology Innovation Commission of Shenzhen(JCYJ20180507182035270,JCYJ20200109114018750).
文摘The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.
基金J.Wang acknowledges the support by MOE,Singapore Ministry of Education(MOE2018-T2-2-095)for research work conducted at the National University of Singapore.Z.L.Liu acknowledges the A*STAR’s Central Research Funds(CRF)Award(Project:SC25/21-111312)+1 种基金Y.Gao acknowledges financial support by ST Engineering Advanced Material Engineering Pte.Ltd.and Singapore Economic Development BoardOpen access funding provided by Shanghai Jiao Tong University
文摘Rechargeable batteries of high energy density and overall performance are becoming a critically important technology in the rapidly changing society of the twenty-first century.While lithium-ion batteries have so far been the dominant choice,numerous emerging applications call for higher capacity,better safety and lower costs while maintaining sufficient cyclability.The design space for potentially better alternatives is extremely large,with numerous new chemistries and architectures being simultaneously explored.These include other insertion ions(e.g.sodium and numerous multivalent ions),conversion electrode materials(e.g.silicon,metallic anodes,halides and chalcogens)and aqueous and solid electrolytes.However,each of these potential“beyond lithium-ion”alternatives faces numerous challenges that often lead to very poor cyclability,especially at the commercial cell level,while lithium-ion batteries continue to improve in performance and decrease in cost.This review examines fundamental principles to rationalise these numerous developments,and in each case,a brief overview is given on the advantages,advances,remaining challenges preventing cell-level implementation and the state-of-the-art of the solutions to these challenges.Finally,research and development results obtained in academia are compared to emerging commercial examples,as a commentary on the current and near-future viability of these“beyond lithium-ion”alternatives.
基金National Natural Science Foundation of China(61925104,62031011,62201157)Major Key Project of PCL+1 种基金China Postdoctoral Science Foundation(2021M700025)National Postdoctoral Program for Innovative Talents(BX2021082).
文摘Visible light communication(VLC)has emerged as a promising communication method in 6G.However,the development of receiving devices is much slower than that of transmitting devices,limited by materials,structures,and fabrication.In this paper,we propose and fabricate an InGaN/GaN multiple-quantum-well-based vertical-structure micro-LED-based photodetector(μPD)on a Si substrate.A comprehensive comparison of the photoelectrical performance and communication performance of three sizes ofμPDs,10,50,and 100μm,is presented.The peak responsivity of all threeμPDs is achieved at 400 nm,while the passband full-widths at half maxima are 87,72,and 78 nm for 10,50,and 100μmμPDs,respectively.The−20 dB cutoff bandwidth is up to 822 MHz for 50μmμPD.A data rate of 10.14 Gbps is experimentally demonstrated by bit and power loading discrete multitone modulation and the proposed digital pre-equalizer algorithm over 1 m free space utilizing the self-designed 4×450μmμPD array as a receiver and a 450 nm laser diode as a transmitter.This is the first time a more than 10 Gbps VLC system has been achieved utilizing a GaN-based micro-PD,to the best of our knowledge.The investigation fully demonstrates the superiority of Si substrates and vertical structures in InGaN/GaNμPDs and shows its great potential for high-speed VLC links beyond 10 Gbps.
