Graphene field-effect transistors(GFET) have attracted much attention in the radio frequency(RF) and microwave fields because of its extremely high carrier mobility. In this paper, a GFET with a gate length of 5 μm i...Graphene field-effect transistors(GFET) have attracted much attention in the radio frequency(RF) and microwave fields because of its extremely high carrier mobility. In this paper, a GFET with a gate length of 5 μm is fabricated through the van der Walls(vdW) transfer process, and then the existing large-signal GFET model is described, and the model is implemented in Verilog-A for analysis in RF and microwave circuits. Next a double-balanced mixer based on four GFETs is designed and analyzed in advanced design system(ADS) tools. Finally, the simulation results show that with the input of 300 and 280 MHz,the IIP3 of the mixed signal is 24.5 dBm.展开更多
Surface wrinkling, a film bonded on a pre-strained elastomeric substrate can form periodic wrinkling patterns, is a common phenomenon in daily life. In existing theoretical models, the film is much thinner than the su...Surface wrinkling, a film bonded on a pre-strained elastomeric substrate can form periodic wrinkling patterns, is a common phenomenon in daily life. In existing theoretical models, the film is much thinner than the substrate so that the substrate can be considered to be elastomeric with infinite thickness. In this paper, the effect of finite substrate thickness is analyzed theoretically for free boundary condition cases. Based on the minimum potential energy principle, a theoretical model is established, and the wave length and amplitude of the wrinkling pattern are obtained. When the thickness of the substrate is more than 200 times larger than the thickness of the film, the results of this study agree well with the results obtained from the previous models for infinite substrate thickness. However, for thin substrates, the effect of finite substrate thickness becomes significant. The model given in this paper accurately describes the effect of finite substrate thickness, providing important design guidelines for future thin-film-on-substrate systems such as stretchable electronic devices.展开更多
Utilizing electrocatalytic CO_(2)reduction(ECR)to decrease the carbon footprint has been regarded as a promising pathway.Herein,we report the synthesis of Ni nanoclusters(NCs)of below 2 nm highly dispersed on N-doped ...Utilizing electrocatalytic CO_(2)reduction(ECR)to decrease the carbon footprint has been regarded as a promising pathway.Herein,we report the synthesis of Ni nanoclusters(NCs)of below 2 nm highly dispersed on N-doped carbon using a Ni/Zn bimetallic metal-organic framework(MOF)precursor.The size and the content of the Ni catalyst can be effectively controlled by varying the Ni:Zn ratio in MOF precursors.The-NH2 group in MOF ligand critically influences the size of Ni catalyst,as well as the property of the carbon substrate.At the optimum ratio of 1:150,Ni NCs with an average size of 1.9 nm anchored on pyridinic N-rich carbon were obtained after MOF pyrolysis.The resultant catalyst exhibits a high Faradaic efficiency for CO(FECO,98.7%)and considerable partial current density for CO(JCO,−40.4 mA·cm^(−2))at−0.88 V versus reversible hydrogen electrode(RHE).Benefiting from the synergistic effect of small Ni clusters and their optimal interaction with the carbon support,the catalyst displays exceptional long-term stability.Density functional theory(DFT)calculations carried out for the three model structures confirm that Ni NCs anchored on N-doped carbon facilitate the easier formation of*COOH intermediate and faster electron transfer rate compared with the large-sized Ni particles represented by Ni(111)and the N-doped carbon without Ni.展开更多
The powder samples of Ca_(9)Sc(PO_(4))_(7):xDy^(^(3+))white emitting phosphors were prepared via a solid state reaction technique.The Ca_(9)Sc(PO_(4))_(7):Dy^(3+)samples were researched by using the GSAS Rietveld refi...The powder samples of Ca_(9)Sc(PO_(4))_(7):xDy^(^(3+))white emitting phosphors were prepared via a solid state reaction technique.The Ca_(9)Sc(PO_(4))_(7):Dy^(3+)samples were researched by using the GSAS Rietveld refinement and X-ray diffraction(XRD) methods,and SEM images and elemental maps were recorded.Under 350 nm excitatio n,the emission spectra of Ca_(9)Sc(PO_(4))_(7):xDy^(3+)samples have two obvious peaks and one weak peak at 484,572 and660 nm,corresponding to the characteristic electron transitions of(^(4)F_(9/2)→ ^(6)H_(15/2),blue),(^(4)F_(9/2)→ ^(6)H_(13/2),yellow) and(^(4)F_(9/2)→ 6 H11/2,red),respectively.The concentration quenching effect,decay lifetime and thermal quenching of the as-synthesized Ca_(9)Sc(PO_(4))_(7):Dy^(3+)samples were researched systematically.The Ca_(9)Sc(PO_(4))_(7):0.02 Dy^(3+)phosphor possesses a good thermal stability,of which the emission intensity at 423 K can maintain 79% of the initial value(273 K).In addition,through the study of the chro maticity coordinates of the Ca_(9)Sc(PO_(4))_(7):0.02 Dy^(3+)phosphor,it is found that it is located in the white region,and the Commission Internationalede L’Eclairage(CIE) chromaticity coordinates are(0.339,0.389),The above results show that Ca_(9)Sc(PO_(4))_(7):xDy^(3+)phosphors can be excellent candidate material for applications in NUV-excited white LEDs.展开更多
We present an Er-doped fiber(Er:fiber)-based femtosecond laser at 780 nm with 256 MHz repetition rate, 191 fs pulse duration, and over 1 W average power.Apart from the careful third-order dispersion management, we int...We present an Er-doped fiber(Er:fiber)-based femtosecond laser at 780 nm with 256 MHz repetition rate, 191 fs pulse duration, and over 1 W average power.Apart from the careful third-order dispersion management, we introduce moderate self-phase modulation to broaden the output spectrum of the Er:fiber amplifier and achieve 193 fs pulse duration and 2.43W average power.Over 40% frequency doubling efficiency is obtained by a periodically poled lithium niobate crystal.Delivering through a hollow-core photonic bandgap fiber, this robust laser becomes an ideal and convenient light source for two-photon autofluorescence imaging.展开更多
Heavily doped colloidal plasmonic nanocrystals have attracted great attention because of their lower and adjustable free carrier densities and tunable localized surface plasmonic resonance bands in the spectral range ...Heavily doped colloidal plasmonic nanocrystals have attracted great attention because of their lower and adjustable free carrier densities and tunable localized surface plasmonic resonance bands in the spectral range from near-infra to mid-infra wavelengths.With its plasmon-enhanced optical nonlinearity,this new family of plasmonic materials shows a huge potential for nonlinear optical applications,such as ultrafast switching,nonlinear sensing,and pulse laser generation.Cu3-xP nanocrystals were previously shown to have a strong saturable absorption at the plasmonic resonance,which enabled high-energy Q-switched fiber lasers with 6.1μs pulse duration.This work demonstrates that both high-quality mode-locked and Q-switched pulses at 1560 nm can be generated by evanescently incorporating two-dimensional(2D)Cu3-xP nanocrystals onto a D-shaped optical fiber as an effective saturable absorber.The 3 dB bandwidth of the mode-locking optical spectrum is as broad as 7.3 nm,and the corresponding pulse duration can reach 423 fs.The repetition rate of the Q-switching pulses is higher than 80 kHz.Moreover,the largest pulse energy is more than 120μJ.Note that laser characteristics are highly stable and repeatable based on the results of over 20 devices.This work may trigger further investigations on heavily doped plasmonic 2D nanocrystals as a next-generation,inexpensive,and solution-processed element for fascinating photonics and optoelectronics applications.展开更多
44.6 fs pulses from a 257 MHz, mode-locked non-polarization maintaining Er-doped fiber laser based on a biased nonlinear amplifying loop mirror are reported. The output power is 104 mW and the single-pulse energy is 0...44.6 fs pulses from a 257 MHz, mode-locked non-polarization maintaining Er-doped fiber laser based on a biased nonlinear amplifying loop mirror are reported. The output power is 104 mW and the single-pulse energy is 0.4 nJ. The minimum pulse duration of the direct output is 44.6 fs, which is the shortest in this kind of laser.展开更多
A series of Eu^(2+)/Dy^(3+) single doped and co-doped Na_(3)Sc_(2)(PO_(4))_(3) phosphors were synthesized by the high-temperature solid-state method,and their phase,morphology,and luminescence properties were characte...A series of Eu^(2+)/Dy^(3+) single doped and co-doped Na_(3)Sc_(2)(PO_(4))_(3) phosphors were synthesized by the high-temperature solid-state method,and their phase,morphology,and luminescence properties were characterized.Under the excitation of 370 nm,the Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+) phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483,577,and 672 nm,respectively.There is energy transfer from Eu^(2+)to Dy^(3+)ion in Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+) phosphor due to the good overlap between the emission spectrum of Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+) and the excitation spectrum of Na_(3)Sc_(2)(PO_(4))_(3):Dy^(3+),which is further confirmed by the fluorescence lifetime decrease of Eu^(2+)ion with the increase of Dy^(3+) concentration.The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory.By increasing the Dy^(3+)concentration,the color coordinates of the Na_(3)Sc_(2)(PO_(4))_(3):0.01Eu^(2+),xDy^(3+)phosphors can be adjusted from blue to white,and then to yellow.The optimized concentration of Dy^(3+)ions is 4.0 mol%,beyond which the concentration quenching will take place.The Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+)phosphor shows fairly good resistance to thermal quenching behavior,of which the emission intensity at 423 K can maintain 90.3%of the initial value(298 K).These results suggest that the Na_(3)Sc_(2)(PO_(4))_(3):0.01Eu^(2+),xDy^(3+)phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.展开更多
基金National Natural Science Foundation of China(Grant Nos.51925208,61974157,61851401,62122082)Key Research Project of Frontier Science,Chinese Academy of Sciences(QYZDB-SSW-JSC021)+3 种基金Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB30030000)National Science and Technology Major Project(2016ZX02301003)Science and Technology Innovation Action Plan of Shanghai Science and Technology Committee(20501130700)Science and Technology Commission of Shanghai Municipality(19JC1415500)。
文摘Graphene field-effect transistors(GFET) have attracted much attention in the radio frequency(RF) and microwave fields because of its extremely high carrier mobility. In this paper, a GFET with a gate length of 5 μm is fabricated through the van der Walls(vdW) transfer process, and then the existing large-signal GFET model is described, and the model is implemented in Verilog-A for analysis in RF and microwave circuits. Next a double-balanced mixer based on four GFETs is designed and analyzed in advanced design system(ADS) tools. Finally, the simulation results show that with the input of 300 and 280 MHz,the IIP3 of the mixed signal is 24.5 dBm.
基金Project supported by the National Natural Science Foundation of China(Nos.11572022 and 11172022)
文摘Surface wrinkling, a film bonded on a pre-strained elastomeric substrate can form periodic wrinkling patterns, is a common phenomenon in daily life. In existing theoretical models, the film is much thinner than the substrate so that the substrate can be considered to be elastomeric with infinite thickness. In this paper, the effect of finite substrate thickness is analyzed theoretically for free boundary condition cases. Based on the minimum potential energy principle, a theoretical model is established, and the wave length and amplitude of the wrinkling pattern are obtained. When the thickness of the substrate is more than 200 times larger than the thickness of the film, the results of this study agree well with the results obtained from the previous models for infinite substrate thickness. However, for thin substrates, the effect of finite substrate thickness becomes significant. The model given in this paper accurately describes the effect of finite substrate thickness, providing important design guidelines for future thin-film-on-substrate systems such as stretchable electronic devices.
基金supported by Nanyang Technological University and the Singapore National Research Foundation(NRF)under its Campus for Research Excellence and Technological Enterprise(CREATE)program through the Cambridge Center for Advanced Research and Education in Singapore(CARES)Cambridge Center for Carbon Reduction in Chemical Technology(C4T)and through CARES and the Berkeley Educational Alliance for Research in Singapore(BEARS)eCO2P program.X.D.W.acknowledge the financial support from Natural Science Foundation of Jiangsu Province(No.BK20200711).
文摘Utilizing electrocatalytic CO_(2)reduction(ECR)to decrease the carbon footprint has been regarded as a promising pathway.Herein,we report the synthesis of Ni nanoclusters(NCs)of below 2 nm highly dispersed on N-doped carbon using a Ni/Zn bimetallic metal-organic framework(MOF)precursor.The size and the content of the Ni catalyst can be effectively controlled by varying the Ni:Zn ratio in MOF precursors.The-NH2 group in MOF ligand critically influences the size of Ni catalyst,as well as the property of the carbon substrate.At the optimum ratio of 1:150,Ni NCs with an average size of 1.9 nm anchored on pyridinic N-rich carbon were obtained after MOF pyrolysis.The resultant catalyst exhibits a high Faradaic efficiency for CO(FECO,98.7%)and considerable partial current density for CO(JCO,−40.4 mA·cm^(−2))at−0.88 V versus reversible hydrogen electrode(RHE).Benefiting from the synergistic effect of small Ni clusters and their optimal interaction with the carbon support,the catalyst displays exceptional long-term stability.Density functional theory(DFT)calculations carried out for the three model structures confirm that Ni NCs anchored on N-doped carbon facilitate the easier formation of*COOH intermediate and faster electron transfer rate compared with the large-sized Ni particles represented by Ni(111)and the N-doped carbon without Ni.
基金Project supported by the National Key Research and Development Program of China(2018YFD0901505)the Science and Technology Cooperation Program between Jilin Province and Chinese Academy of Sciences(2019SYHZ0008)。
文摘The powder samples of Ca_(9)Sc(PO_(4))_(7):xDy^(^(3+))white emitting phosphors were prepared via a solid state reaction technique.The Ca_(9)Sc(PO_(4))_(7):Dy^(3+)samples were researched by using the GSAS Rietveld refinement and X-ray diffraction(XRD) methods,and SEM images and elemental maps were recorded.Under 350 nm excitatio n,the emission spectra of Ca_(9)Sc(PO_(4))_(7):xDy^(3+)samples have two obvious peaks and one weak peak at 484,572 and660 nm,corresponding to the characteristic electron transitions of(^(4)F_(9/2)→ ^(6)H_(15/2),blue),(^(4)F_(9/2)→ ^(6)H_(13/2),yellow) and(^(4)F_(9/2)→ 6 H11/2,red),respectively.The concentration quenching effect,decay lifetime and thermal quenching of the as-synthesized Ca_(9)Sc(PO_(4))_(7):Dy^(3+)samples were researched systematically.The Ca_(9)Sc(PO_(4))_(7):0.02 Dy^(3+)phosphor possesses a good thermal stability,of which the emission intensity at 423 K can maintain 79% of the initial value(273 K).In addition,through the study of the chro maticity coordinates of the Ca_(9)Sc(PO_(4))_(7):0.02 Dy^(3+)phosphor,it is found that it is located in the white region,and the Commission Internationalede L’Eclairage(CIE) chromaticity coordinates are(0.339,0.389),The above results show that Ca_(9)Sc(PO_(4))_(7):xDy^(3+)phosphors can be excellent candidate material for applications in NUV-excited white LEDs.
基金supported in part by the National Natural Science Foundation of China(Nos.61475008and 31327901)
文摘We present an Er-doped fiber(Er:fiber)-based femtosecond laser at 780 nm with 256 MHz repetition rate, 191 fs pulse duration, and over 1 W average power.Apart from the careful third-order dispersion management, we introduce moderate self-phase modulation to broaden the output spectrum of the Er:fiber amplifier and achieve 193 fs pulse duration and 2.43W average power.Over 40% frequency doubling efficiency is obtained by a periodically poled lithium niobate crystal.Delivering through a hollow-core photonic bandgap fiber, this robust laser becomes an ideal and convenient light source for two-photon autofluorescence imaging.
基金the support from the National Key Research&Development Program(No.2016YFA0201902)Shenzhen Nanshan District Pilotage Team Program(No.LHTD20170006)+1 种基金Australian Research Council(ARC,FT 150100450,IH150100006,and CE170100039)the funding support from China Postdoctoral Science Foundation Grant(No.217M622758).
文摘Heavily doped colloidal plasmonic nanocrystals have attracted great attention because of their lower and adjustable free carrier densities and tunable localized surface plasmonic resonance bands in the spectral range from near-infra to mid-infra wavelengths.With its plasmon-enhanced optical nonlinearity,this new family of plasmonic materials shows a huge potential for nonlinear optical applications,such as ultrafast switching,nonlinear sensing,and pulse laser generation.Cu3-xP nanocrystals were previously shown to have a strong saturable absorption at the plasmonic resonance,which enabled high-energy Q-switched fiber lasers with 6.1μs pulse duration.This work demonstrates that both high-quality mode-locked and Q-switched pulses at 1560 nm can be generated by evanescently incorporating two-dimensional(2D)Cu3-xP nanocrystals onto a D-shaped optical fiber as an effective saturable absorber.The 3 dB bandwidth of the mode-locking optical spectrum is as broad as 7.3 nm,and the corresponding pulse duration can reach 423 fs.The repetition rate of the Q-switching pulses is higher than 80 kHz.Moreover,the largest pulse energy is more than 120μJ.Note that laser characteristics are highly stable and repeatable based on the results of over 20 devices.This work may trigger further investigations on heavily doped plasmonic 2D nanocrystals as a next-generation,inexpensive,and solution-processed element for fascinating photonics and optoelectronics applications.
基金supported in part by the National Natural Science Foundation of China(Nos.1162780027,31327901,and 61761136002)the Major National Basic Research Program of China(No.2013CB922401)the National Key Scientific Instrument and Equipment Development Program(No.2012YQ140005)
文摘44.6 fs pulses from a 257 MHz, mode-locked non-polarization maintaining Er-doped fiber laser based on a biased nonlinear amplifying loop mirror are reported. The output power is 104 mW and the single-pulse energy is 0.4 nJ. The minimum pulse duration of the direct output is 44.6 fs, which is the shortest in this kind of laser.
基金Project supported by the National Key Research and Development Program of China(2019YFA0709101)the Science and Technology Cooperation Program between Jilin Province and Chinese Academy of Sciences(2019SYHZ0008)R&D Projects in Key Areas of Guangdong Province(2020B0101010001)。
文摘A series of Eu^(2+)/Dy^(3+) single doped and co-doped Na_(3)Sc_(2)(PO_(4))_(3) phosphors were synthesized by the high-temperature solid-state method,and their phase,morphology,and luminescence properties were characterized.Under the excitation of 370 nm,the Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+) phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483,577,and 672 nm,respectively.There is energy transfer from Eu^(2+)to Dy^(3+)ion in Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+) phosphor due to the good overlap between the emission spectrum of Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+) and the excitation spectrum of Na_(3)Sc_(2)(PO_(4))_(3):Dy^(3+),which is further confirmed by the fluorescence lifetime decrease of Eu^(2+)ion with the increase of Dy^(3+) concentration.The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory.By increasing the Dy^(3+)concentration,the color coordinates of the Na_(3)Sc_(2)(PO_(4))_(3):0.01Eu^(2+),xDy^(3+)phosphors can be adjusted from blue to white,and then to yellow.The optimized concentration of Dy^(3+)ions is 4.0 mol%,beyond which the concentration quenching will take place.The Na_(3)Sc_(2)(PO_(4))_(3):Eu^(2+),Dy^(3+)phosphor shows fairly good resistance to thermal quenching behavior,of which the emission intensity at 423 K can maintain 90.3%of the initial value(298 K).These results suggest that the Na_(3)Sc_(2)(PO_(4))_(3):0.01Eu^(2+),xDy^(3+)phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.
