Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microf...Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.展开更多
Laser induced breakdown spectroscopy (LIBS) provides a useful technique for food security as well as determining nutrition contents. In this paper, optical emission studies of laser induced plasma on commercial tea ...Laser induced breakdown spectroscopy (LIBS) provides a useful technique for food security as well as determining nutrition contents. In this paper, optical emission studies of laser induced plasma on commercial tea samples were carried out. The spectral intensities of Mg, Mn, Ca, A1, C and CN vibration bands varying with laser energy and the detection delay time of an intensified charge coupled device were studied. In addition, the relative concentrations of six microelements, i.e., Mg, Mn, Ca, Al, Na and K, were analyzed semi-quantitatively as well as H, for four kinds of tea samples. Moreover, the plasma parameters were explored, including electron temperature and electron number density. The electron temperature and electron number density were around 11000 K and 1017 cm-3, respectively. The results show that it is reasonable to consider the LIBS technique as a new method for analyzing the compositions of tea leaf samples.展开更多
An experimental setup of laser-induced graphite plasma was built and the spectral characteristics and properties of graphite plasma were studied. From the temporal behavior of graphite plasma, the duration of CN parti...An experimental setup of laser-induced graphite plasma was built and the spectral characteristics and properties of graphite plasma were studied. From the temporal behavior of graphite plasma, the duration of CN partials (B2 ∑+ →-X2 ∑+) emission was two times longer than that of atomic carbon, and all intensities reached the maximum during the early stage from 0.2 μs to 0.8 μs. The electron temperature decreased from 11807 K to 8755 K, the vibration temperature decreased from 8973 K to 6472 K, and the rotational temperature decreased from 7288 K to 4491 K with the delay time, respectively. The effect of the laser energy was also studied, and it was found that the thresholds and spectral characteristics of CN molecular and C atomic spectroscopy presented great differences. At lower laser energies, the electron excited temperature, the electron density, the vibrational temperature and rotational temperature of CN partials increased rapidly. At higher laser energies, the increasing of electron excited temperature and electron density slow down, and the vibrational temperature and rotational temperature even trend to saturation due to plasma shielding and dissociation of CN molecules. The relationship among the three kinds of temperatures was Telec〉Tvib〉Trot at the same time. The electron density of the graphite plasma was in the order of 1017 cm-3 and 1018 cm-3.展开更多
With the wide application of laser welding technology in automobiles and rail transportation, the non-destructive testing technology for laser welding seams is also getting better. Aiming at the laser welding seam of ...With the wide application of laser welding technology in automobiles and rail transportation, the non-destructive testing technology for laser welding seams is also getting better. Aiming at the laser welding seam of two-layer metal sheet below 3 mm, the possibility of laser welding seam detection by air-coupling ultrasonic detection technology is discussed. By numerical analysis and experimental analysis,Lamb wave is excited on aluminum plate in air. Through the propagation simulation of Lamb wave in laser weld specimen, the influence of laser weld width and weld quality on reflectivity and transmittance is analyzed. The propagation law of Lamb wave in laser weld specimen is clarified. The results show that the quality of laser weld can be evaluated by the mode of Lamb wave A0.展开更多
A two-dimensional(2D)surface-enhanced Raman scattering(SERS)substrate is fabricated by decorating carbon nanotube(CNT)films with Ag nanoparticles(Ag NPs)in different sizes,via simple and low-cost chemical reduction me...A two-dimensional(2D)surface-enhanced Raman scattering(SERS)substrate is fabricated by decorating carbon nanotube(CNT)films with Ag nanoparticles(Ag NPs)in different sizes,via simple and low-cost chemical reduction method and self-assembling method.The change of Raman and SERS activity of carbon nanotubes/Ag nanoparticles(CNTs/Ag NPs)composites with varying size of Ag NPs are investigated by using rhodamine 6G(R6G)as a probe molecule.Meanwhile,the scattering cross section of Ag NPs and the distribution of electric field of CNTs/Ag NPs composite are simulated through finite difference time domain(FDTD)method.Surface plasmon resonance(SPR)wavelength is redshifted as the size of Ag NPs increases,and the intensity of SERS and electric field increase with Ag NPs size increasing.The experiment and simulation results show a Raman scattering enhancement factor(EF)of 108for the hybrid substrate.展开更多
Plasma density and temperature can be diagnosed by x-ray line emission measurement with crystal,and bent crystals such as von Hamos and Hall structures are proposed to improve the diffraction brightness.In this study,...Plasma density and temperature can be diagnosed by x-ray line emission measurement with crystal,and bent crystals such as von Hamos and Hall structures are proposed to improve the diffraction brightness.In this study,a straightforward solution for the focusing schemes of flat and bent crystals is provided.Simulations with XOP code are performed to validate the analytical model,and good agreements are achieved.The von Hamos or multi-cone crystal can lead to several hundred times intensity enhancements for a 200μm plasma source.This model benefits the applications of the focusing bent crystals.展开更多
Top-emitting organic light-emitting diodes(TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display.However,the efficiency roll-off at high brightness is the issue that needs to be ...Top-emitting organic light-emitting diodes(TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display.However,the efficiency roll-off at high brightness is the issue that needs to be resolved for further practical applications using TEOLED devices.Herein,a serial of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as a charge generation layer is demonstrated.With unique photovoltaic properties,the charge generation layer can absorb part of the photons emitted by the emission layer(Ir(ppy)3) and generate electrons and holes.By optimizing the thickness of the charge generation layer,the pure green electroluminescent TEOLED device manufactured has a high brightness of 156 000 cd/cm^(2) and a maximum current efficiency of 86 cd/A.Importantly,relying on the energy between the photovoltaic and the microcavity effects,only 1.5% of the efficiency roll-off is obtained at 1 000—10 000 cd/cm^(2).Introducing fullerene/zinc-phthalocyanine as the charge-generating layer provides a promising alternative for developing high-efficiency tandem TEOLED devices.展开更多
Tuning the photoresponse of monolayer MoS_(2) could extend its potential application in many fields,however,it is still a challenge.In this study,CsPbBr_(3) nanoparticles were prepared and spin-coated on the surface o...Tuning the photoresponse of monolayer MoS_(2) could extend its potential application in many fields,however,it is still a challenge.In this study,CsPbBr_(3) nanoparticles were prepared and spin-coated on the surface of monolayer MoS_(2) to fabricate hybrid CsPbBr_(3)/MoS_(2) photodetectors.By combing the photoelectrical property of the CsPbBr_(3),the synergistic effect has been systematically studied from its carrier mobility,photoresponse and detectivity.It was found that nanofilm-coating of CsPbBr_(3)would impede the photoelectric performance due to the electron-hole recombination facilitated by the defects at the interface of C PbBr_(3) and MoS_(2) films.While the nanoparticles decorating was observed to significantly improve the conductivity of the monolayer Mo S_(2),which also increased the on/off ratio of the MoS_(2) transistor from 8.2×10~3 to 4.4×10^(4),and enhanced the carrier mobility from 0.090 cm^(2)V^(-1)s^(-1)to 0.202 cm^(2)V^(-1)s^(-1),ascribing to a mixed electron recombination-injection process.Furthermore,the CsPbBr_(3) nanofilm would decrease the responsivity to 136 and 178 A/W under the light wavelength of 400 and 500 nm,respectively,while decorating CsPbBr_(3) nanoparticles improve the photoresponse to 948 and 883 A/W with the detectivity at the level of 10^(11)Jones.This work may provide an easy and cost-efficient way to tune the photoresponse of MoS_(2) photodetectors.展开更多
A reflective beam splitter is proposed and verified. The unit cell of the beam splitter is composed of a metal pattern, a dielectric substrate, and a metallic ground. Each subarray structure of the device is composed ...A reflective beam splitter is proposed and verified. The unit cell of the beam splitter is composed of a metal pattern, a dielectric substrate, and a metallic ground. Each subarray structure of the device is composed of four unit cells, which are gradually rotated at 45°. The horizontal and vertical subarrays form a 4×4 gradient metasurface supercell. In the operating frequency band, the incident linearly polarized terahertz wave is reflected and divided into four beams of approximately equal power but different propagation directions. The proposed terahertz beam splitter based on metasurface has the advantages of small size, low cost and easy processing, and can be applied to terahertz stealth and imaging.展开更多
In this study,a toroidal quartz(2023)crystal is designed for monochromatic X-ray imaging at 72.3◦.The designed crystal produces excellent images of a laser-produced plasma emitting He-like Ti X-rays at 4.75 keV.Based ...In this study,a toroidal quartz(2023)crystal is designed for monochromatic X-ray imaging at 72.3◦.The designed crystal produces excellent images of a laser-produced plasma emitting He-like Ti X-rays at 4.75 keV.Based on the simulations,the imaging resolutions of the spherical and toroidal crystals in the sagittal direction are found to be 15 and 5μm,respectively.Moreover,the simulation results show that a higher resolution image of the source can be obtained by using a toroidal crystal.An X-ray backlight imaging experiment is conducted using 4.75 keV He-like Ti X-rays,a 3×3 metal grid,an imaging plate and a toroidal quartz crystal with a lattice constant of 2d=0.2749 nm.The meridional and sagittal radii of the toroidalα-quartz crystal are 295.6 and 268.5 mm,respectively.A highly resolved image of the microgrid,with a spatial resolution of 10μm,is obtained in the experiment.By using similar toroidal crystal designs,the application of a spatially resolved spectrometer with high-resolution X-ray imaging ability is capable of providing imaging data with the same magnification ratio in the sagittal and meridional planes.展开更多
Chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional nanomaterials.When multiple precursors are induced,the CVD process often gives rise to the growth of dop...Chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional nanomaterials.When multiple precursors are induced,the CVD process often gives rise to the growth of doped or alloy compounds.In this work,we demonstrate the self-assembly of a variety of‘phase-separated’functional nanostructures from a single CVD in the presence of various precursors.In specific,with silicon substrate and powder of Mn and SnTe as precursors,we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles,Mn11Si19 nanowires,and SnTe nanoplates.The Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along the<111>direction of the crystalline Si via an Au-catalyzed vapor-liquid-solid process,in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder,respectively.In contrast,direct vapor-solid deposition led to particle-free<110>-oriented Si/SiOx core-shell nanowires and<100>-oriented Mn11Si19 nanowires,a promising thermoelectric material.No Sn or Te impurities were detected in these nanostructures down to the experimental limit.Topological crystalline insulator SnTe nanoplates with dominant{100}and{111}facets were found to be free of Mn(and Si)impurities,although nanoparticles and nanowires containing Mn were found in the vicinity of the nanoplates.While multiple-channel transport was observed in the SnTe nanoplates,it may not be related to the topological surface states due to surface oxidation.Finally,we carried out thermodynamic analysis and density functional theory calculations to understand the‘phase-separation’phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.展开更多
Buffer-modified C_(60)/pentacene as charge generation layer(CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes(OLEDs) with...Buffer-modified C_(60)/pentacene as charge generation layer(CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes(OLEDs) with multiple identical emissive units and using buffer-modified C_(60)/pentacene organic semiconductor heterojunction(OHJ) as CGL are demonstrated to exhibit better current density and brightness, compared with conventional single-unit devices. The current density and brightness both can be significantly improved with increasing the thickness of Al. However, excessive thickness of Al seriously decreases the transmittance of films and damages the interface. As a result, the maximum current efficiency of 1.43 cd·A^(-1) at 30 mA ·cm^(-2) can be achieved for tandem OLEDs with optimal thickness of Al. These results clearly demonstrate that Cs_2CO_3/Al is an effective buffer for C_(60)/pentacene-based tandem OLEDs.展开更多
In spectral diagnostic physics experiments of inertial confinement fusion, the spectral signal is weak due to the low diffraction efficiency when using bent crystals. A spectral diagnostic instrument with high efficie...In spectral diagnostic physics experiments of inertial confinement fusion, the spectral signal is weak due to the low diffraction efficiency when using bent crystals. A spectral diagnostic instrument with high efficiency and wide spectral range is urgently needed. A multi-curvature bent crystal with multi-energy focusing ability is proposed based on the traditional conical crystal geometry. It has advantages of wide spectral range, strong focusing ability, and high spectral resolution. It also can eliminate the imaging aberration in principle due to rotational symmetry for the incoming X rays. A spectral diagnostic experiment based on a fabricated multi-curvatureα-quartz crystal was accomplished using a titanium X-ray tube of the bent crystal, and the corresponding experimental data using a plane α-quartz crystal was also acquired to demonstrate the strong focusing ability.The result shows that the Kα intensity of the multi-curvature α-quartz crystal is 157 times greater than that of the plane crystal, and the corresponding energy range is about 4.51–5.14 keV. This diagnostic instrument could be combined with a streak camera at a vertical direction so as to intensify the diffracted X-ray signal with a wide spectral range.展开更多
We report a Tm-doped noise-like mode-locked(NLML)pulsed fiber laser with a compact linear cavity which consists of dual nonlinear optical loop mirrors(NOLMs).The design of dual-NOLM shows both exceptional compactness ...We report a Tm-doped noise-like mode-locked(NLML)pulsed fiber laser with a compact linear cavity which consists of dual nonlinear optical loop mirrors(NOLMs).The design of dual-NOLM shows both exceptional compactness in construction and distinct flexibility.In this laser,mode-locking can be realized through the nonlinear optical loop mirror technique.Stable noise-like mode-locked pulses with spectral bandwidth of 29.18 nm and pulse energy of 46 nJ are generated at a central wavelength of 1999.7 nm.Our results indicate that such a simple and inexpensive structure can pave the way for the development of generating supercontinuum with desirable performance.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304409 and 61705028)the Natural Science Foundation of Chongqing City,China(Grant Nos.csct2013jcyjA4004 and cstc2017jcyjA0893)+1 种基金the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ1500422)the Postgraduate Research Innovation Foundation of Chongqing City,China(Grant No.CYS17240)
文摘Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.
基金supported by National Natural Science Foundation of China(No.61205149)the Scientific and Technological Talents Training Project of Chongqing,China(No.CSTC2013kjrc-qnrc40002)+1 种基金the Scientific and Technological Project of Nan'an District(2011)the Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology at Chongqing University,China(No.2007DA10512714409)
文摘Laser induced breakdown spectroscopy (LIBS) provides a useful technique for food security as well as determining nutrition contents. In this paper, optical emission studies of laser induced plasma on commercial tea samples were carried out. The spectral intensities of Mg, Mn, Ca, A1, C and CN vibration bands varying with laser energy and the detection delay time of an intensified charge coupled device were studied. In addition, the relative concentrations of six microelements, i.e., Mg, Mn, Ca, Al, Na and K, were analyzed semi-quantitatively as well as H, for four kinds of tea samples. Moreover, the plasma parameters were explored, including electron temperature and electron number density. The electron temperature and electron number density were around 11000 K and 1017 cm-3, respectively. The results show that it is reasonable to consider the LIBS technique as a new method for analyzing the compositions of tea leaf samples.
基金supported by National Natural Science Foundation of China(No.61205149)Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry,Science Research Funds of Chongqing Municipal Education Commission(KJ1500436)+2 种基金Scientific and Technological Talents Training Project of Chongqing(CSTC2013kjrc-qnrc40002)Key Project of Foundation and Advanced Technology Research Project of Chongqing(CSTC2015jcyj B0358)Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology(2007DA10512714409)
文摘An experimental setup of laser-induced graphite plasma was built and the spectral characteristics and properties of graphite plasma were studied. From the temporal behavior of graphite plasma, the duration of CN partials (B2 ∑+ →-X2 ∑+) emission was two times longer than that of atomic carbon, and all intensities reached the maximum during the early stage from 0.2 μs to 0.8 μs. The electron temperature decreased from 11807 K to 8755 K, the vibration temperature decreased from 8973 K to 6472 K, and the rotational temperature decreased from 7288 K to 4491 K with the delay time, respectively. The effect of the laser energy was also studied, and it was found that the thresholds and spectral characteristics of CN molecular and C atomic spectroscopy presented great differences. At lower laser energies, the electron excited temperature, the electron density, the vibrational temperature and rotational temperature of CN partials increased rapidly. At higher laser energies, the increasing of electron excited temperature and electron density slow down, and the vibrational temperature and rotational temperature even trend to saturation due to plasma shielding and dissociation of CN molecules. The relationship among the three kinds of temperatures was Telec〉Tvib〉Trot at the same time. The electron density of the graphite plasma was in the order of 1017 cm-3 and 1018 cm-3.
文摘With the wide application of laser welding technology in automobiles and rail transportation, the non-destructive testing technology for laser welding seams is also getting better. Aiming at the laser welding seam of two-layer metal sheet below 3 mm, the possibility of laser welding seam detection by air-coupling ultrasonic detection technology is discussed. By numerical analysis and experimental analysis,Lamb wave is excited on aluminum plate in air. Through the propagation simulation of Lamb wave in laser weld specimen, the influence of laser weld width and weld quality on reflectivity and transmittance is analyzed. The propagation law of Lamb wave in laser weld specimen is clarified. The results show that the quality of laser weld can be evaluated by the mode of Lamb wave A0.
基金the National Natural Science Foundation of China(Grant No.61875024)the Natural Science Foundation of Chongqing,China(Grant Nos.cstc2019jcyjmsxm X0639 and cstc2020jcyj-msxm0605)the Scientific and Technology Research Program of Chongqing Municipal Education Commission,China(Grant Nos.KJQN202000648 and KJQN201900602)。
文摘A two-dimensional(2D)surface-enhanced Raman scattering(SERS)substrate is fabricated by decorating carbon nanotube(CNT)films with Ag nanoparticles(Ag NPs)in different sizes,via simple and low-cost chemical reduction method and self-assembling method.The change of Raman and SERS activity of carbon nanotubes/Ag nanoparticles(CNTs/Ag NPs)composites with varying size of Ag NPs are investigated by using rhodamine 6G(R6G)as a probe molecule.Meanwhile,the scattering cross section of Ag NPs and the distribution of electric field of CNTs/Ag NPs composite are simulated through finite difference time domain(FDTD)method.Surface plasmon resonance(SPR)wavelength is redshifted as the size of Ag NPs increases,and the intensity of SERS and electric field increase with Ag NPs size increasing.The experiment and simulation results show a Raman scattering enhancement factor(EF)of 108for the hybrid substrate.
基金Project supported by the National Natural Science Fundation of China(Grant Nos.11775203 and 12075219)the China Academy of Engineering Physics(CAEP)Foundation(Grant No.CX20210019).
文摘Plasma density and temperature can be diagnosed by x-ray line emission measurement with crystal,and bent crystals such as von Hamos and Hall structures are proposed to improve the diffraction brightness.In this study,a straightforward solution for the focusing schemes of flat and bent crystals is provided.Simulations with XOP code are performed to validate the analytical model,and good agreements are achieved.The von Hamos or multi-cone crystal can lead to several hundred times intensity enhancements for a 200μm plasma source.This model benefits the applications of the focusing bent crystals.
基金supported by the National Natural Science Foundation of China (Nos.22072010)the Science and Technology Research Program of Chongqing Municipal Education Commission (Nos.KJQN202100610,KJQN202100611 and KJQN202100613)+1 种基金the Doctor Research Start-up Funding of Chongqing University of Post and Telecommunications (No.E012A2020018)the Postdoctoral Project of Chongqing Science and Technology Bureau (No.cstc2021jcyj-bsh0250)。
文摘Top-emitting organic light-emitting diodes(TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display.However,the efficiency roll-off at high brightness is the issue that needs to be resolved for further practical applications using TEOLED devices.Herein,a serial of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as a charge generation layer is demonstrated.With unique photovoltaic properties,the charge generation layer can absorb part of the photons emitted by the emission layer(Ir(ppy)3) and generate electrons and holes.By optimizing the thickness of the charge generation layer,the pure green electroluminescent TEOLED device manufactured has a high brightness of 156 000 cd/cm^(2) and a maximum current efficiency of 86 cd/A.Importantly,relying on the energy between the photovoltaic and the microcavity effects,only 1.5% of the efficiency roll-off is obtained at 1 000—10 000 cd/cm^(2).Introducing fullerene/zinc-phthalocyanine as the charge-generating layer provides a promising alternative for developing high-efficiency tandem TEOLED devices.
基金financially supported by the National Natural Science Foundation of China (Nos. 52002254, 52272160)Sichuan Science and Technology Foundation (Nos. 2020YJ0262, 2021YFH0127, 2022YFH0083, 2022YFSY0045)+2 种基金the Chunhui plan of Ministry of Education, Fundamental Research Funds for the Central Universities, China (No. YJ201893)the Open-Foundation of Key Laboratory of Laser Device Technology, China North Industries Group Corporation Limited (No. KLLDT202104)Supported by the fund of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP202210)。
文摘Tuning the photoresponse of monolayer MoS_(2) could extend its potential application in many fields,however,it is still a challenge.In this study,CsPbBr_(3) nanoparticles were prepared and spin-coated on the surface of monolayer MoS_(2) to fabricate hybrid CsPbBr_(3)/MoS_(2) photodetectors.By combing the photoelectrical property of the CsPbBr_(3),the synergistic effect has been systematically studied from its carrier mobility,photoresponse and detectivity.It was found that nanofilm-coating of CsPbBr_(3)would impede the photoelectric performance due to the electron-hole recombination facilitated by the defects at the interface of C PbBr_(3) and MoS_(2) films.While the nanoparticles decorating was observed to significantly improve the conductivity of the monolayer Mo S_(2),which also increased the on/off ratio of the MoS_(2) transistor from 8.2×10~3 to 4.4×10^(4),and enhanced the carrier mobility from 0.090 cm^(2)V^(-1)s^(-1)to 0.202 cm^(2)V^(-1)s^(-1),ascribing to a mixed electron recombination-injection process.Furthermore,the CsPbBr_(3) nanofilm would decrease the responsivity to 136 and 178 A/W under the light wavelength of 400 and 500 nm,respectively,while decorating CsPbBr_(3) nanoparticles improve the photoresponse to 948 and 883 A/W with the detectivity at the level of 10^(11)Jones.This work may provide an easy and cost-efficient way to tune the photoresponse of MoS_(2) photodetectors.
基金supported by the New Direction Cultivation Project of Chongqing University of Posts and Telecommunications (No.A2014-116)the Key Research Program of Chongqing University of Posts and Telecommunications on Interdisciplinary and Emerging Field (No.A2018-01)。
文摘A reflective beam splitter is proposed and verified. The unit cell of the beam splitter is composed of a metal pattern, a dielectric substrate, and a metallic ground. Each subarray structure of the device is composed of four unit cells, which are gradually rotated at 45°. The horizontal and vertical subarrays form a 4×4 gradient metasurface supercell. In the operating frequency band, the incident linearly polarized terahertz wave is reflected and divided into four beams of approximately equal power but different propagation directions. The proposed terahertz beam splitter based on metasurface has the advantages of small size, low cost and easy processing, and can be applied to terahertz stealth and imaging.
基金supported by the National Natural Science Foundation of China(Nos.61604028,11775203,and 12075219)the Chongqing Study Abroad Innovation Fund Project(No.cx2018023)+1 种基金the Plasma Physics Key Laboratory Fund Project(No.6142A04180207)the Innovation and Development Fund of China Academy of Engineering Physics(No.CX20210019)。
文摘In this study,a toroidal quartz(2023)crystal is designed for monochromatic X-ray imaging at 72.3◦.The designed crystal produces excellent images of a laser-produced plasma emitting He-like Ti X-rays at 4.75 keV.Based on the simulations,the imaging resolutions of the spherical and toroidal crystals in the sagittal direction are found to be 15 and 5μm,respectively.Moreover,the simulation results show that a higher resolution image of the source can be obtained by using a toroidal crystal.An X-ray backlight imaging experiment is conducted using 4.75 keV He-like Ti X-rays,a 3×3 metal grid,an imaging plate and a toroidal quartz crystal with a lattice constant of 2d=0.2749 nm.The meridional and sagittal radii of the toroidalα-quartz crystal are 295.6 and 268.5 mm,respectively.A highly resolved image of the microgrid,with a spatial resolution of 10μm,is obtained in the experiment.By using similar toroidal crystal designs,the application of a spatially resolved spectrometer with high-resolution X-ray imaging ability is capable of providing imaging data with the same magnification ratio in the sagittal and meridional planes.
基金This work was supported,in part,by the Indiana University Vice Provost for Research through the Faculty Research Support Program,National Science Foundation Research Experience for Undergraduates grant PHY-1757646,NSF-DMR-1350002We thank the Indiana University-Bloomington Nanoscale Characterization Facility(NCF)for the use of instruments(The XPS instrument at NCF was funded through grant NSF-DMR-1126394).
文摘Chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional nanomaterials.When multiple precursors are induced,the CVD process often gives rise to the growth of doped or alloy compounds.In this work,we demonstrate the self-assembly of a variety of‘phase-separated’functional nanostructures from a single CVD in the presence of various precursors.In specific,with silicon substrate and powder of Mn and SnTe as precursors,we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles,Mn11Si19 nanowires,and SnTe nanoplates.The Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along the<111>direction of the crystalline Si via an Au-catalyzed vapor-liquid-solid process,in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder,respectively.In contrast,direct vapor-solid deposition led to particle-free<110>-oriented Si/SiOx core-shell nanowires and<100>-oriented Mn11Si19 nanowires,a promising thermoelectric material.No Sn or Te impurities were detected in these nanostructures down to the experimental limit.Topological crystalline insulator SnTe nanoplates with dominant{100}and{111}facets were found to be free of Mn(and Si)impurities,although nanoparticles and nanowires containing Mn were found in the vicinity of the nanoplates.While multiple-channel transport was observed in the SnTe nanoplates,it may not be related to the topological surface states due to surface oxidation.Finally,we carried out thermodynamic analysis and density functional theory calculations to understand the‘phase-separation’phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.
基金supported by the Natural Science Foundation of Chongqing (CSTB2023NSCQ-MSX0687, cstc2021jcyjmsxm X0736, and cstc2021jcyj-msxm X0930)“Chunhui” Plan Cooperative Scientific Research Project of the Ministry of Education of China(HZKY20220214)+7 种基金China Postdoctoral Science Foundation (2021M691487)the National Natural Science Foundation of China (62305037, 62375032,61975023, 62375276, 62375060, and 22072010)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202200544, KJQN202100510 and KJQN202100507)the Project of Chongqing Normal University Foundation (20XLB034)Shanghai Pilot Program for Basic Research (22JC1403200)the National Key Research and Development Program of China (2018YFB2200500 and 2022YFA1604403)the Open Fund of the State Key Laboratory of High Field Laser Physics(Shanghai Institute of Optics and Fine Mechanics)the Innovation and Entrepreneurship Training Program for College Students (S202210637047,S202210637042, and S2022051101220)。
基金supported by the National Nature Science Foundation of China(No.61604027)the Scientific and Technological Research Foundation of Chongqing Municipal Education Commission(Nos.KJ1400411 and KJ1600439),the Scientific and Technological Research Foundation of Chongqing Municipal Education Commission(No.KJ1500404)+1 种基金the Youth Natural Science Foundation of Chongqing University of Posts and Telecommunications(No.A2013-39)the Basic and Advanced Technology Research Project of Chongqing Municipality(No.cstc2016jcyA 1923)
文摘Buffer-modified C_(60)/pentacene as charge generation layer(CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes(OLEDs) with multiple identical emissive units and using buffer-modified C_(60)/pentacene organic semiconductor heterojunction(OHJ) as CGL are demonstrated to exhibit better current density and brightness, compared with conventional single-unit devices. The current density and brightness both can be significantly improved with increasing the thickness of Al. However, excessive thickness of Al seriously decreases the transmittance of films and damages the interface. As a result, the maximum current efficiency of 1.43 cd·A^(-1) at 30 mA ·cm^(-2) can be achieved for tandem OLEDs with optimal thickness of Al. These results clearly demonstrate that Cs_2CO_3/Al is an effective buffer for C_(60)/pentacene-based tandem OLEDs.
基金supported in part by the National Natural Science Foundation of China (Nos. 61604028 and61804019)the Venture&Innovation Support Program for Chongqing Overseas Returnees (No. cx2018023)the Science and Technology on Plasmas Physics Laboratory (No. 6142A04180207)。
文摘In spectral diagnostic physics experiments of inertial confinement fusion, the spectral signal is weak due to the low diffraction efficiency when using bent crystals. A spectral diagnostic instrument with high efficiency and wide spectral range is urgently needed. A multi-curvature bent crystal with multi-energy focusing ability is proposed based on the traditional conical crystal geometry. It has advantages of wide spectral range, strong focusing ability, and high spectral resolution. It also can eliminate the imaging aberration in principle due to rotational symmetry for the incoming X rays. A spectral diagnostic experiment based on a fabricated multi-curvatureα-quartz crystal was accomplished using a titanium X-ray tube of the bent crystal, and the corresponding experimental data using a plane α-quartz crystal was also acquired to demonstrate the strong focusing ability.The result shows that the Kα intensity of the multi-curvature α-quartz crystal is 157 times greater than that of the plane crystal, and the corresponding energy range is about 4.51–5.14 keV. This diagnostic instrument could be combined with a streak camera at a vertical direction so as to intensify the diffracted X-ray signal with a wide spectral range.
基金supported by the Nature Science Foundation of Chongqing(No.cstc2018jcyjAX0585)。
文摘We report a Tm-doped noise-like mode-locked(NLML)pulsed fiber laser with a compact linear cavity which consists of dual nonlinear optical loop mirrors(NOLMs).The design of dual-NOLM shows both exceptional compactness in construction and distinct flexibility.In this laser,mode-locking can be realized through the nonlinear optical loop mirror technique.Stable noise-like mode-locked pulses with spectral bandwidth of 29.18 nm and pulse energy of 46 nJ are generated at a central wavelength of 1999.7 nm.Our results indicate that such a simple and inexpensive structure can pave the way for the development of generating supercontinuum with desirable performance.