We investigate theoretically the single-photon scattering by a A-type three-level system interacting with a whispering-gallery-type resonator which is coupled to a one-dimensional waveguide by full quantum-mechanical ...We investigate theoretically the single-photon scattering by a A-type three-level system interacting with a whispering-gallery-type resonator which is coupled to a one-dimensional waveguide by full quantum-mechanical approach. The single-photon transmission amplitude and reflection amplitude are obtained exactly via real-space approach. The single-photon transport properties controlling by classic optical field are discussed. The critical coupling condition in the coupled waveguide-whispering-gallery resonator-atom with three-level system is also analyzed.展开更多
We investigate theoretically the voltage-controlled single-photon transport properties in a one-dimensional waveguide.The transmission and reflection amplitudes are obtained by a full quantum-mechanical approach.It is...We investigate theoretically the voltage-controlled single-photon transport properties in a one-dimensional waveguide.The transmission and reflection amplitudes are obtained by a full quantum-mechanical approach.It is revealed that one can control the single photon transmitted or reflected by adjusting the bias voltage.This scheme may have applications in the design of optoelectronic devices.展开更多
We develop a master equation approach to describe the dynamics of distant resonators coupled through a one-dimensional waveguide. Our method takes into account the back-actions of the reservoirs, and enables us to cal...We develop a master equation approach to describe the dynamics of distant resonators coupled through a one-dimensional waveguide. Our method takes into account the back-actions of the reservoirs, and enables us to calculate the exact dynamics of the complete system at all times. We show that such system can cause nonexponential and long-lived photon decay due to the existence of a relaxation effect. The physical origin of non-Markovianity in our model system is the finite propagation speed resulting in time delays in communication between the nodes, and strong decay rate of the emitters into the waveguide. When the distance satisfies the standing wave condition, we find that when the time delay is increased, the dark modes formation is no longer perfect, and the average photon number of dark mode decreases in steady time limit.展开更多
Two types of one-dimensional(1D)anti-PT-symmetric periodic ring optical waveguide networks,consisting of gain and loss materials,are constructed.The singular optical propagation properties of these networks are invest...Two types of one-dimensional(1D)anti-PT-symmetric periodic ring optical waveguide networks,consisting of gain and loss materials,are constructed.The singular optical propagation properties of these networks are investigated.The results show that the system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection.Conversely,the system composed of loss materials demonstrates equal transmittance and reflectance at some frequencies.In both the systems,a new type of total reflection phenomenon is observed.When the imaginary part of the refractive indices of waveguide segments is smaller than 10-5,the system shows bidirectional transparency with the transmittance tending to be 1 and reflectivity to be smaller than 10-8 at some bands.When the refractive indices of the waveguide segments are real,the system will be bidirectional transparent at the full band.These findings may deepen the understanding of anti-PT-symmetric optical systems and optical waveguide networks,and possess potential applications in efficient optical energy storage,ultra-sensitive optical filters,ultra-sensitive all-optical switches,integrated optical chips,stealth physics,and so on.展开更多
We analyze the transport property of a single photon in a one-dimensional coupled resonator waveguide coupled with a Λ-type emitter assisted by an additional cavity. The reflection and transmission coefficients of th...We analyze the transport property of a single photon in a one-dimensional coupled resonator waveguide coupled with a Λ-type emitter assisted by an additional cavity. The reflection and transmission coefficients of the inserted photon are obtained by the stationary theory. It is shown that the polarization state of the inserted photon can be converted with high efficiency. This study may inspire single-photon devices for scalable quantum memory.展开更多
In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are c...In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are closely related to the hydrogen bonds(H-bonds)network between water molecules.Therefore,it is crucial to analyze the relationship between these two aspects.In this paper,the infrared spectrum and motion characteristics of the stretching vibrations of the O-H bonds in one-dimensional confined water(1DCW)and bulk water(BW)in(6,6)single-walled carbon nanotubes(SWNT)are studied by molecular dynamics simulations.The results show that the stretching vibrations of the two O-H bonds in 1DCW exhibit different frequencies in the infrared spectrum,while the O-H bonds in BW display two identical main frequency peaks.Further analysis using the spring oscillator model reveals that the difference in the stretching amplitude of the O-H bonds is the main factor causing the change in vibration frequency,where an increase in stretching amplitude leads to a decrease in spring stiffness and,consequently,a lower vibration frequency.A more in-depth study found that the interaction of H-bonds between water molecules is the fundamental cause of the increased stretching amplitude and decreased vibration frequency of the O-H bonds.Finally,by analyzing the motion trajectory of the H atoms,the dynamic differences between 1DCW and BW are clearly revealed.These findings provide a new perspective for understanding the behavior of water molecules at the nanoscale and are of significant importance in advancing the development of infrared spectroscopy detection technology.展开更多
In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particul...In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.展开更多
[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,...[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.展开更多
This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conv...This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conversion of laser energy into THz waves.Through meticulous investigation,valuable insights into optimizing THz generation processes for practical applications were unearthed.By investigating Hertz potentials,an eigen-value equation for the solutions of the guided modes(i.e.,eigenvalues)was found.The effects of various param-eters,including the effective mode index and the laser pulse power,on the electric field components of THz radia-tion,including the fundamental TE(transverse electric)and TM(transverse magnetic)modes,were evaluated.By analyzing these factors,this research elucidated the nuanced mechanisms governing THz wave generation within cylindrical GaAs waveguides,paving the way for refined methodologies and enhanced efficiency.The sig-nificance of cylindrical GaAs waveguides extends beyond their roles as mere facilitators of THz generation;their design and fabrication hold the key to unlocking the potential for compact and portable THz systems.This trans-formative capability not only amplifies the efficiency of THz generation but also broadens the horizons of practical applications.展开更多
Using the Bose-Fermi mapping method,we obtain the exact ground state wavefunction of one-dimensional(1D)Bose gas with the zero-range dipolar interaction in the strongly repulsive contact interaction limit.Its ground s...Using the Bose-Fermi mapping method,we obtain the exact ground state wavefunction of one-dimensional(1D)Bose gas with the zero-range dipolar interaction in the strongly repulsive contact interaction limit.Its ground state density distributions for both repulsive and attractive dipole interactions are exhibited.It is shown that in the case of the finite dipole interaction the density profiles do not change obviously with the increase of dipole interaction and display the typical shell structure of Tonks-Girardeau gases.As the repulsive dipole interaction is greatly strong,the density decreases at the center of the trap and displays a sunken valley.As the attractive dipole interaction increases,the density displays more oscillations and sharp peaks appear in the strong attraction limit,which mainly originate from the atoms occupying the low single particle levels.展开更多
Two-dimensional(2D)transition metal sulfides(TMDs)are emerging and highly well received 2D materials,which are considered as an ideal 2D platform for studying various electronic properties and potential applications d...Two-dimensional(2D)transition metal sulfides(TMDs)are emerging and highly well received 2D materials,which are considered as an ideal 2D platform for studying various electronic properties and potential applications due to their chemical diversity.Converting 2D TMDs into one-dimensional(1D)TMDs nanotubes can not only retain some advantages of 2D nanosheets but also providing a unique direction to explore the novel properties of TMDs materials in the 1D limit.However,the controllable preparation of high-quality nanotubes remains a major challenge.It is very necessary to review the advanced development of one-dimensional transition metal dichalcogenide nanotubes from preparation to application.Here,we first summarize a series of bottom-up synthesis methods of 1D TMDs,such as template growth and metal catalyzed method.Then,top-down synthesis methods are summarized,which included selfcuring and stacking of TMDs nanosheets.In addition,we discuss some key applications that utilize the properties of 1D-TMDs nanotubes in the areas of catalyst preparation,energy storage,and electronic devices.Last but not least,we prospect the preparation methods of high-quality 1D-TMDs nanotubes,which will lay a foundation for the synthesis of high-performance optoelectronic devices,catalysts,and energy storage components.展开更多
A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication chan...A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication channels and less antenna sizes,multi-band antennas are currently under intensive investigation.By a novel feeding method,three odd modes are excited on an SSPP waveguide resonator,which performs as an end-fire antenna operating at three bands,7.15-7.26 GHz,11.6-12.2 GHz and 13.5-13.64 GHz.It exhibits reasonably high and stable maximum gains of 5.26 dBi,7.97 dBi and 10.1 dBi and maximum efficiencies of 64%,92%and 98%at the three bands,respectively.Moreover,in the second band,the main beam angle shows a frequency dependence with a total scanning angle of 19°.The miniaturized triple-band antenna has a great potential in wireless communication systems,satellite communication and radar systems.展开更多
The oxygen evolution reaction(OER),a critical half-reaction in water electrolysis,has garnered significant attention.However,sluggish OER kinetics has emerged as a major impediment to efficient electrochemical energy c...The oxygen evolution reaction(OER),a critical half-reaction in water electrolysis,has garnered significant attention.However,sluggish OER kinetics has emerged as a major impediment to efficient electrochemical energy conversion.There is an urgent need to design novel electrocatalysts with optimized OER kinetics and enhanced intrinsic activity to improve overall OER performance.Herein,one-dimensional(1D)nanocomposites with high electrocatalytic activity were developed through the deposition of CoFePBA nanocubes onto the surface of MnO_(2) nanowires.The electronic structure of the nanocomposite surface was modified,and the synergistic effects between transition metals were leveraged to enhance catalytic activity through the deposition of Prussian blue analog(PBA)nanocubes on manganese dioxide nanowires.Specifically,CoFePBA featured an open crystal structure that offiered numerous electrochemical active sites and efficient charge transfer pathways.Additionally,the synergistic interactions between Co and Fe significantly reduced the OER overpotential.Additionally,the 1D rigid MnO_(2) acted as protective armor,ensuring the stability of active sites within CoFePBA during the OER.The synthesized MnO_(2)@CoFePBA achieved an overpotential of 1.614 V at 10 mA/cm^(2) and a small Tafel slope of 94 mV/dec and demonstrated stable performance for over 200 h.This work offers new insights into the rational design of various PBA-based nanocomposites with high activity and stability.展开更多
Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optic...Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optical waveguides is proposed,which shows a simple fabrication process,high upward diffraction efficiency,and lower far-field divergence angle.The measured results of the diffraction grating at a wavelength of 905 nm show the average upward diffraction efficiency of 90.5% and average far-field divergence angle of 0.154°,which shows a good agreement with the design results with the upward diffraction efficiency of 91.6%and far-field divergence angle of 0.105°.展开更多
Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engin...Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.展开更多
Diffractive optical neural networks(DONNs)have exhibited the advantages of parallelization,high speed,and low consumption.However,the existing DONNs based on free-space diffractive optical elements are bulky and unste...Diffractive optical neural networks(DONNs)have exhibited the advantages of parallelization,high speed,and low consumption.However,the existing DONNs based on free-space diffractive optical elements are bulky and unsteady.In this study,we propose a planar-waveguide integrated diffractive neural network chip architecture.The three diffractive layers are engraved on the same side of a quartz wafer.The three-layer chip is designed with 32-mm3 processing space and enables a computing speed of 3.1×109 Tera operations per second.The results show that the proposed chip achieves 73.4%experimental accuracy for the Modified National Institute of Standards and Technology database while showing the system’s robustness in a cycle test.The consistency of experiments is 88.6%,and the arithmetic mean standard deviation of the results is~4.7%.The proposed chip architecture can potentially revolutionize high-resolution optical processing tasks with high robustness.展开更多
We study the thermodynamic properties of the classical one-dimensional generalized nonlinear Klein-Gordon lattice model(n≥2)by using the cluster variation method with linear response theory.The results of this method...We study the thermodynamic properties of the classical one-dimensional generalized nonlinear Klein-Gordon lattice model(n≥2)by using the cluster variation method with linear response theory.The results of this method are exact in the thermodynamic limit.We present the single-site reduced densityρ^((1))(z),averages such as(z^(2)),<|z^(n)|>,and<(z_(1)-z_(2))^(2)>,the specific heat C_(v),and the static correlation functions.We analyze the scaling behavior of these quantities and obtain the exact scaling powers at the low and high temperatures.Using these results,we gauge the accuracy of the projective truncation approximation for theφ^(4)lattice model.展开更多
Compared to existing deformation monitoring methods,landslide early warning can be achieved by detecting precursor signals of slope instability through acoustic emission(AE).Acquisition of AE signals generated by acti...Compared to existing deformation monitoring methods,landslide early warning can be achieved by detecting precursor signals of slope instability through acoustic emission(AE).Acquisition of AE signals generated by active waveguide facilitates monitoring the development of shear surface and provides a foundation for quantifying landslide movement.Backfill particles are the dominant AE sources in active waveguides,typically chosen from materials such as gravels or sands.However,the influence of particle sizes and gradings has not been clarified in existing laboratory models or field monitoring.This research introduces a direct shear test for active waveguide,where spherical glass beads are employed to precisely regulate the size and grading of backfill particles.A programmable logic controller maintains a constant shearing speed and equivalent total deformation.Through a comprehensive analysis of AE,deformation,and mechanical measurements,this study evaluates the impact of particle size and grading on monitoring capabilities.The findings suggest that the AE mechanism in glass beads is attributed to particle collision and dislocation,leading to AE events characterized by low amplitude and energy levels.The percentage of high-amplitude AE events rises steadily with the progression of shearing.The correlation between shear force,cumulative ring down count(RDC)of AE,and deformation conforms to a power function,with the exponent relying on particle size,grading,and shearing speed.Notably,the combination of small particles and low shearing speeds can yield the maximum cumulative RDC,while selecting particles with uneven grading will significantly enhance the intensity of AE signals from active waveguide.展开更多
To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,u...To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,utilizing the reflection of the grating to achieve the electromagnetic-like induced transparency effect at different wavelengths.The high slope characteristics of the EIT-like effect enabled a higher quality factor and sensitivity.The transmission principle of the structure was analyzed using the transmission matrix method,and the transmission spectrum and mode field distribution were simulated using the finite-difference time-domain(FDTD)method,and the device structure parameters were adjusted for optimization.Simulation results show that the proposed structure achieves an EIT-like effect with a quality factor of 59267.5.In the analysis of refractive index sensing characteristics,the structure exhibits a sensitivity of 408.57 nm/RIU and a detection limit of 6.23×10^(-5) RIU.Therefore,the proposed structure achieved both a high quality factor and refractive index sensitivity,demonstrating excellent sensing performance for applications in environmental monitoring,biomedical fields,and other areas with broad market potential.展开更多
Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithiu...Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithium niobate waveguide amplifier achieving>10 dB off-chip(fiber-to-fiber)net gain and>20 mW fiber-output amplified power is demonstrated,thanks to the low-propagation-loss waveguides and robust waveguide edge-couplers prepared by the photolithography assisted chemomechanical etching technique.Systematic investigation on the fabricated waveguide amplifiers reveals remarkable optical gain around the peak wavelength of 1532 nm as well as the low fiber-coupling loss of-1.2 dB/facet.A fiber Bragg-grating based waveguide laser is further demonstrated using the fabricated waveguide amplifier as the external gain chip,which generates>2 mW off-chip power continuous-wave lasing around the gain peak at 1532 nm.The unambiguous demonstration of fiber-to-fiber net gain of the erbium-doped thinfilm lithium niobate(TFLN)waveguide amplifier as well as its external gain chip application will benefit diverse fields demanding scalable gain elements with highspeed tunability.展开更多
基金＊Supported by National Natural Science Foundation of China under Grant Nos. 10874134, 11004001, and 10947115 and Anhui Province for Young Teachers Foundation under Crant No. 2010SQRL037ZD
文摘We investigate theoretically the single-photon scattering by a A-type three-level system interacting with a whispering-gallery-type resonator which is coupled to a one-dimensional waveguide by full quantum-mechanical approach. The single-photon transmission amplitude and reflection amplitude are obtained exactly via real-space approach. The single-photon transport properties controlling by classic optical field are discussed. The critical coupling condition in the coupled waveguide-whispering-gallery resonator-atom with three-level system is also analyzed.
基金by the National Natural Science Foundation of China under Grant No 11004001Anhui Province for Young Teachers Foundation under Grant No 2010SQRL037ZD.
文摘We investigate theoretically the voltage-controlled single-photon transport properties in a one-dimensional waveguide.The transmission and reflection amplitudes are obtained by a full quantum-mechanical approach.It is revealed that one can control the single photon transmitted or reflected by adjusting the bias voltage.This scheme may have applications in the design of optoelectronic devices.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11574041,11475037,and 11704026
文摘We develop a master equation approach to describe the dynamics of distant resonators coupled through a one-dimensional waveguide. Our method takes into account the back-actions of the reservoirs, and enables us to calculate the exact dynamics of the complete system at all times. We show that such system can cause nonexponential and long-lived photon decay due to the existence of a relaxation effect. The physical origin of non-Markovianity in our model system is the finite propagation speed resulting in time delays in communication between the nodes, and strong decay rate of the emitters into the waveguide. When the distance satisfies the standing wave condition, we find that when the time delay is increased, the dark modes formation is no longer perfect, and the average photon number of dark mode decreases in steady time limit.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674107,61475049,11775083,61774062,and 61771205).
文摘Two types of one-dimensional(1D)anti-PT-symmetric periodic ring optical waveguide networks,consisting of gain and loss materials,are constructed.The singular optical propagation properties of these networks are investigated.The results show that the system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection.Conversely,the system composed of loss materials demonstrates equal transmittance and reflectance at some frequencies.In both the systems,a new type of total reflection phenomenon is observed.When the imaginary part of the refractive indices of waveguide segments is smaller than 10-5,the system shows bidirectional transparency with the transmittance tending to be 1 and reflectivity to be smaller than 10-8 at some bands.When the refractive indices of the waveguide segments are real,the system will be bidirectional transparent at the full band.These findings may deepen the understanding of anti-PT-symmetric optical systems and optical waveguide networks,and possess potential applications in efficient optical energy storage,ultra-sensitive optical filters,ultra-sensitive all-optical switches,integrated optical chips,stealth physics,and so on.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674094,11474092,and 11774089)
文摘We analyze the transport property of a single photon in a one-dimensional coupled resonator waveguide coupled with a Λ-type emitter assisted by an additional cavity. The reflection and transmission coefficients of the inserted photon are obtained by the stationary theory. It is shown that the polarization state of the inserted photon can be converted with high efficiency. This study may inspire single-photon devices for scalable quantum memory.
基金Supported by the Natural Science Foundation of China(51705326,52075339)。
文摘In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are closely related to the hydrogen bonds(H-bonds)network between water molecules.Therefore,it is crucial to analyze the relationship between these two aspects.In this paper,the infrared spectrum and motion characteristics of the stretching vibrations of the O-H bonds in one-dimensional confined water(1DCW)and bulk water(BW)in(6,6)single-walled carbon nanotubes(SWNT)are studied by molecular dynamics simulations.The results show that the stretching vibrations of the two O-H bonds in 1DCW exhibit different frequencies in the infrared spectrum,while the O-H bonds in BW display two identical main frequency peaks.Further analysis using the spring oscillator model reveals that the difference in the stretching amplitude of the O-H bonds is the main factor causing the change in vibration frequency,where an increase in stretching amplitude leads to a decrease in spring stiffness and,consequently,a lower vibration frequency.A more in-depth study found that the interaction of H-bonds between water molecules is the fundamental cause of the increased stretching amplitude and decreased vibration frequency of the O-H bonds.Finally,by analyzing the motion trajectory of the H atoms,the dynamic differences between 1DCW and BW are clearly revealed.These findings provide a new perspective for understanding the behavior of water molecules at the nanoscale and are of significant importance in advancing the development of infrared spectroscopy detection technology.
基金Supported by the National Natural Science Foundation of China(62105039)。
文摘In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.
基金National Key Research and Development Program of China(2022YFF0707602)National Natural Science Foundation of China(62471097,62471115,62471101)National Natural Science Foundation of Sichuan(2025ZNSFSC0537)。
文摘[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
文摘This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conversion of laser energy into THz waves.Through meticulous investigation,valuable insights into optimizing THz generation processes for practical applications were unearthed.By investigating Hertz potentials,an eigen-value equation for the solutions of the guided modes(i.e.,eigenvalues)was found.The effects of various param-eters,including the effective mode index and the laser pulse power,on the electric field components of THz radia-tion,including the fundamental TE(transverse electric)and TM(transverse magnetic)modes,were evaluated.By analyzing these factors,this research elucidated the nuanced mechanisms governing THz wave generation within cylindrical GaAs waveguides,paving the way for refined methodologies and enhanced efficiency.The sig-nificance of cylindrical GaAs waveguides extends beyond their roles as mere facilitators of THz generation;their design and fabrication hold the key to unlocking the potential for compact and portable THz systems.This trans-formative capability not only amplifies the efficiency of THz generation but also broadens the horizons of practical applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174026)。
文摘Using the Bose-Fermi mapping method,we obtain the exact ground state wavefunction of one-dimensional(1D)Bose gas with the zero-range dipolar interaction in the strongly repulsive contact interaction limit.Its ground state density distributions for both repulsive and attractive dipole interactions are exhibited.It is shown that in the case of the finite dipole interaction the density profiles do not change obviously with the increase of dipole interaction and display the typical shell structure of Tonks-Girardeau gases.As the repulsive dipole interaction is greatly strong,the density decreases at the center of the trap and displays a sunken valley.As the attractive dipole interaction increases,the density displays more oscillations and sharp peaks appear in the strong attraction limit,which mainly originate from the atoms occupying the low single particle levels.
基金supported by the National Natural Science Foundation of China(No.22202065).
文摘Two-dimensional(2D)transition metal sulfides(TMDs)are emerging and highly well received 2D materials,which are considered as an ideal 2D platform for studying various electronic properties and potential applications due to their chemical diversity.Converting 2D TMDs into one-dimensional(1D)TMDs nanotubes can not only retain some advantages of 2D nanosheets but also providing a unique direction to explore the novel properties of TMDs materials in the 1D limit.However,the controllable preparation of high-quality nanotubes remains a major challenge.It is very necessary to review the advanced development of one-dimensional transition metal dichalcogenide nanotubes from preparation to application.Here,we first summarize a series of bottom-up synthesis methods of 1D TMDs,such as template growth and metal catalyzed method.Then,top-down synthesis methods are summarized,which included selfcuring and stacking of TMDs nanosheets.In addition,we discuss some key applications that utilize the properties of 1D-TMDs nanotubes in the areas of catalyst preparation,energy storage,and electronic devices.Last but not least,we prospect the preparation methods of high-quality 1D-TMDs nanotubes,which will lay a foundation for the synthesis of high-performance optoelectronic devices,catalysts,and energy storage components.
基金supported in part by the Natural Science Foundation of Tianjin(No.19JCYBJC16100)the Tianjin Innovation and Entrepreneurship Training Program(No.202210060027)。
文摘A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication channels and less antenna sizes,multi-band antennas are currently under intensive investigation.By a novel feeding method,three odd modes are excited on an SSPP waveguide resonator,which performs as an end-fire antenna operating at three bands,7.15-7.26 GHz,11.6-12.2 GHz and 13.5-13.64 GHz.It exhibits reasonably high and stable maximum gains of 5.26 dBi,7.97 dBi and 10.1 dBi and maximum efficiencies of 64%,92%and 98%at the three bands,respectively.Moreover,in the second band,the main beam angle shows a frequency dependence with a total scanning angle of 19°.The miniaturized triple-band antenna has a great potential in wireless communication systems,satellite communication and radar systems.
基金supported by the National Natural Science Foundation of China(No.52371240)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘The oxygen evolution reaction(OER),a critical half-reaction in water electrolysis,has garnered significant attention.However,sluggish OER kinetics has emerged as a major impediment to efficient electrochemical energy conversion.There is an urgent need to design novel electrocatalysts with optimized OER kinetics and enhanced intrinsic activity to improve overall OER performance.Herein,one-dimensional(1D)nanocomposites with high electrocatalytic activity were developed through the deposition of CoFePBA nanocubes onto the surface of MnO_(2) nanowires.The electronic structure of the nanocomposite surface was modified,and the synergistic effects between transition metals were leveraged to enhance catalytic activity through the deposition of Prussian blue analog(PBA)nanocubes on manganese dioxide nanowires.Specifically,CoFePBA featured an open crystal structure that offiered numerous electrochemical active sites and efficient charge transfer pathways.Additionally,the synergistic interactions between Co and Fe significantly reduced the OER overpotential.Additionally,the 1D rigid MnO_(2) acted as protective armor,ensuring the stability of active sites within CoFePBA during the OER.The synthesized MnO_(2)@CoFePBA achieved an overpotential of 1.614 V at 10 mA/cm^(2) and a small Tafel slope of 94 mV/dec and demonstrated stable performance for over 200 h.This work offers new insights into the rational design of various PBA-based nanocomposites with high activity and stability.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB2802401)the Beijing Municipal Natural Science Foundation(Grant No.Z221100006722002).
文摘Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optical waveguides is proposed,which shows a simple fabrication process,high upward diffraction efficiency,and lower far-field divergence angle.The measured results of the diffraction grating at a wavelength of 905 nm show the average upward diffraction efficiency of 90.5% and average far-field divergence angle of 0.154°,which shows a good agreement with the design results with the upward diffraction efficiency of 91.6%and far-field divergence angle of 0.105°.
基金supported by the UK’s Engineering and Physical Sciences Research Council(Grant Nos.EP/V000624/1,EP/X03495X/1,EP/X041166/1,and EP/T02643X/1)the Royal Society(Grant No.RG\R2\232531).
文摘Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.62175050 and U2341245)the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2024054).
文摘Diffractive optical neural networks(DONNs)have exhibited the advantages of parallelization,high speed,and low consumption.However,the existing DONNs based on free-space diffractive optical elements are bulky and unsteady.In this study,we propose a planar-waveguide integrated diffractive neural network chip architecture.The three diffractive layers are engraved on the same side of a quartz wafer.The three-layer chip is designed with 32-mm3 processing space and enables a computing speed of 3.1×109 Tera operations per second.The results show that the proposed chip achieves 73.4%experimental accuracy for the Modified National Institute of Standards and Technology database while showing the system’s robustness in a cycle test.The consistency of experiments is 88.6%,and the arithmetic mean standard deviation of the results is~4.7%.The proposed chip architecture can potentially revolutionize high-resolution optical processing tasks with high robustness.
基金supported by the National Natural Science Foundation of China(Grant No.11974420).
文摘We study the thermodynamic properties of the classical one-dimensional generalized nonlinear Klein-Gordon lattice model(n≥2)by using the cluster variation method with linear response theory.The results of this method are exact in the thermodynamic limit.We present the single-site reduced densityρ^((1))(z),averages such as(z^(2)),<|z^(n)|>,and<(z_(1)-z_(2))^(2)>,the specific heat C_(v),and the static correlation functions.We analyze the scaling behavior of these quantities and obtain the exact scaling powers at the low and high temperatures.Using these results,we gauge the accuracy of the projective truncation approximation for theφ^(4)lattice model.
基金funding support from the National Natural Science Foundation of China(Grant No.52404224)Beijing Natural Science Foundation(Grant No.8244051)the fellowship of China National Postdoctoral Program for Innovative Talents(Grant No.BX20230175).
文摘Compared to existing deformation monitoring methods,landslide early warning can be achieved by detecting precursor signals of slope instability through acoustic emission(AE).Acquisition of AE signals generated by active waveguide facilitates monitoring the development of shear surface and provides a foundation for quantifying landslide movement.Backfill particles are the dominant AE sources in active waveguides,typically chosen from materials such as gravels or sands.However,the influence of particle sizes and gradings has not been clarified in existing laboratory models or field monitoring.This research introduces a direct shear test for active waveguide,where spherical glass beads are employed to precisely regulate the size and grading of backfill particles.A programmable logic controller maintains a constant shearing speed and equivalent total deformation.Through a comprehensive analysis of AE,deformation,and mechanical measurements,this study evaluates the impact of particle size and grading on monitoring capabilities.The findings suggest that the AE mechanism in glass beads is attributed to particle collision and dislocation,leading to AE events characterized by low amplitude and energy levels.The percentage of high-amplitude AE events rises steadily with the progression of shearing.The correlation between shear force,cumulative ring down count(RDC)of AE,and deformation conforms to a power function,with the exponent relying on particle size,grading,and shearing speed.Notably,the combination of small particles and low shearing speeds can yield the maximum cumulative RDC,while selecting particles with uneven grading will significantly enhance the intensity of AE signals from active waveguide.
基金supported by Natural Science Foundation of Gansu Province(NO.21JR7RA289)。
文摘To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,utilizing the reflection of the grating to achieve the electromagnetic-like induced transparency effect at different wavelengths.The high slope characteristics of the EIT-like effect enabled a higher quality factor and sensitivity.The transmission principle of the structure was analyzed using the transmission matrix method,and the transmission spectrum and mode field distribution were simulated using the finite-difference time-domain(FDTD)method,and the device structure parameters were adjusted for optimization.Simulation results show that the proposed structure achieves an EIT-like effect with a quality factor of 59267.5.In the analysis of refractive index sensing characteristics,the structure exhibits a sensitivity of 408.57 nm/RIU and a detection limit of 6.23×10^(-5) RIU.Therefore,the proposed structure achieved both a high quality factor and refractive index sensitivity,demonstrating excellent sensing performance for applications in environmental monitoring,biomedical fields,and other areas with broad market potential.
基金financial supports from National Key R&D Program of China(Grant No.2022YFA1205100,2022YFA1404600)National Natural Science Foundation of China(Grant Nos.12192251,12334014,12474325,12134001,12304418,12474378,12274133,12174107,12174113,12274130)+2 种基金the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301403)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Fundamental Research Funds for the Central Universities,the Engineering Research Center for Nanophotonics&Advanced Instrument,Ministry of Education,East China Normal University(No.2023nmc005).
文摘Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithium niobate waveguide amplifier achieving>10 dB off-chip(fiber-to-fiber)net gain and>20 mW fiber-output amplified power is demonstrated,thanks to the low-propagation-loss waveguides and robust waveguide edge-couplers prepared by the photolithography assisted chemomechanical etching technique.Systematic investigation on the fabricated waveguide amplifiers reveals remarkable optical gain around the peak wavelength of 1532 nm as well as the low fiber-coupling loss of-1.2 dB/facet.A fiber Bragg-grating based waveguide laser is further demonstrated using the fabricated waveguide amplifier as the external gain chip,which generates>2 mW off-chip power continuous-wave lasing around the gain peak at 1532 nm.The unambiguous demonstration of fiber-to-fiber net gain of the erbium-doped thinfilm lithium niobate(TFLN)waveguide amplifier as well as its external gain chip application will benefit diverse fields demanding scalable gain elements with highspeed tunability.
