Characterizing the petrophysical properties holds significant importance in shale oil reservoirs.Twodimensional(2-D)nuclear magnetic resonance(NMR),a nondestructive and noninvasive technique,has numerous applications ...Characterizing the petrophysical properties holds significant importance in shale oil reservoirs.Twodimensional(2-D)nuclear magnetic resonance(NMR),a nondestructive and noninvasive technique,has numerous applications in petrophysical characterization.However,the complex occurrence states of the fluids and the highly non-uniform distributions of minerals and organic matter pose challenges in the NMR-based petrophysical characterization.A novel T_(1)-T_(2)relaxation theory is introduced for the first time in this study.The transverse and longitudinal relaxivities of pore fluids are determined based on numerical investigation and experimental analysis.Additionally,an improved random walk algorithm is proposed to,on the basis of digital shale core,simulate the effects of the hydrogen index(HI)for the organic matter,echo spacing(T_(E)),pyrite content,clay mineral type,and clay content on T_(1)-T_(2)spectra at different NMR frequencies.Furthermore,the frequency conversion cross-plots for various petrophysical parameters influenced by the above factors are established.This study provides new insights into NMRbased petrophysical characterization and the frequency conversion of petrophysical parameters measured by laboratory NMR instruments and NMR logging in shale oil reservoirs.It is of great significance for the efficient exploration and environmentally friendly production of shale oil.展开更多
Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting t...Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting their potential applications.Therefore,it is imperative to study the creation of lowfrequency signals using antennas with suitable dimensions.In contrast to conventional mechanical antenna techniques,our study generates low-frequency signals in the spatial domain utilizing the principle of the Doppler effect.We also defines the antenna array architecture,the timing sequency,and the radiating element signal waveform,and provides experimental prototypes including 8/64 antennas based on earlier research.In the conducted experiments,121 MHz,40 MHz,and 10 kHz composite signals are generated by 156 MHz radiating element signals.The composite signal spectrum matches the simulations,proving our low-frequency signal generating method works.This holds significant implications for research on generating low-frequency signals with small-sized antennas.展开更多
The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the re...The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the real-space Hamiltonian. The calculated results show that the probability of single photon frequency down-or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling.We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon. The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown. Our results may be useful in designing quantum devices at the single-photon level.展开更多
The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-...The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-band is realized by combining with the local oscillator and the power control circuit to complete functions such as amplification, filtering and gain. In order to achieve the performance optimization and a high level of integration of the Ku-band monolithic microwave integrated circuits(MMIC) operating chip, the 3 D vertical interconnection micro-assembly technology is used. By stacking solder balls on the printed circuit board(PCB), the technology decreases the volume of the original transceiver to a miniaturized module. The module has a good electromagnetic compatibility through special structure designs. This module has the characteristics of miniaturization, low power consumption and high density, which is suitable for popularization in practical application.展开更多
Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global c...Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global conversion efficiencies in such nonlinear environments has long been considered impossible,here,we formally address this challenge even in scenarios involving a very large number of spatial modes.By utilizing fundamental notions from optical statistical mechanics,we develop a universal theoretical framework that effectively treats all frequency components as chemical reactants/products,capable of undergoing optical thermodynamic reactions facilitated by a variety of multi-wave mixing effects.These photon-photon reactions are governed by conservation laws that directly determine the optical temperatures and chemical potentials of the ensued chemical equilibria for each frequency species.In this context,we develop a comprehensive stoichiometric model and formally derive an expression that relates the chemical potentials to the optical stoichiometric coefficients,in a manner akin to atomic/molecular chemical reactions.This advancement unlocks new predictive capabilities that can facilitate the optimization of frequency generation in highly multimode photonic arrangements,surpassing the limitations of conventional schemes that rely exclusively on nonlinear optical dynamics.Notably,we identify a universal regime of Rayleigh-Jeans thermalization where an optical reaction at near-zero optical temperatures can promote the complete and entropically irreversible conversion of light to the fundamental mode at a target frequency.Our theoretical results are corroborated by numerical simulations in settings where second-harmonic generation,sum-frequency generation and four-wave mixing processes can manifest.展开更多
We experimentally demonstrate multiple frequency conversion via atomic spin coherence of storing a light pulse in a doped solid. The essence of this multiple frequency conversion is four-wave mixing based on stored at...We experimentally demonstrate multiple frequency conversion via atomic spin coherence of storing a light pulse in a doped solid. The essence of this multiple frequency conversion is four-wave mixing based on stored atomic spin coherence. Through electromagnetically induced transparency, an input probe pulse is stored into atomic spin coherence by modulating the intensity of the control field. By using two different control fields to interact with the coherently prepared medium, the stored atomic spin coherence can be transformed into three different information channels. Multiple frequency conversion is implemented efficiently by manipulating the spectra of the control fields to scatter atomic spin coherence. This multiple frequency conversion is expected to have potential applications in information processing and communication network.展开更多
In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-...In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-free frequency conversion of a quantum state can be achieved by injecting a strong signal field. The dependences of conversion efficiency on the pump parameter, extra losses and input state amplitude are also analysed.展开更多
At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment co...At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment control is becoming more and more obvious. Frequency conversion technology has the advantages of regulation and control, etc. The application of this technology in mines can promote the production efficiency of transportation and ventilation. Frequency conversion technology is widely used in modern life. Applying frequency conversion technology to mining equipment in modern coal mine mechanical and electrical engineering can ensure the smooth operation of mechanical and electrical equipment to a great extent. Therefore, this paper will focus on the application of frequency conversion technology in modern coal mine electromechanical engineering.展开更多
The generation of optical vortices in compact systems and across different spectral regions can open new horizons for their applications in end-user devices.Latest advances in the design and fabrication of optical met...The generation of optical vortices in compact systems and across different spectral regions can open new horizons for their applications in end-user devices.Latest advances in the design and fabrication of optical metasurfaces made of a quadratically nonlinear material enable highly precise creation of vortices with different topological charges at the second-harmonic frequency,with the potential to obtain various other structured states of light.展开更多
We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this pro...We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.展开更多
This paper investigates the start-up and shutdown phases of a five-bladed closed-impeller centrifugal pump through experimental analysis,capturing the temporal evolution of its hydraulic performances.The study also pr...This paper investigates the start-up and shutdown phases of a five-bladed closed-impeller centrifugal pump through experimental analysis,capturing the temporal evolution of its hydraulic performances.The study also predicts the transient characteristics of the pump under non-rated operating conditions to assess the accuracy of various machine learning methods in forecasting its instantaneous performance.Results indicate that the pump’s transient behavior in power-frequency mode markedly differs from that in frequency-conversion mode.Specifically,the power-frequency mode achieves steady-state values faster and exhibits smaller fluctuations before stabilization compared to the other mode.During the start-up phase,as the steady-state flow rate increases,inlet and outlet pressures and head also rise,while torque and shaft power decrease,with rotational speed remaining largely unchanged.Conversely,during the shutdown phase,no significant changes were observed in torque,shaft power,or rotational speed.Six machine learning models,including Gaussian Process Regression(GPR),Decision Tree Regression(DTR),and Deep Learning Networks(DLN),demonstrated high accuracy in predicting the hydraulic performance of the centrifugal pump during the start-up and shutdown phases in both power-frequency and frequency-conversion conditions.The findings provide a theoretical foundation for improved prediction of pump hydraulic performance.For instance,when predicting head and flow rate during power-frequency start-up,GPR achieved absolute and relative errors of 0.54 m(7.84%)and 0.21 m3/h(13.57%),respectively,while the Feedforward Neural Network(FNN)reported errors of 0.98 m(8.24%)and 0.10 m3/h(16.71%).By contrast,the Support Vector Machine Regression(SVMR)and Generalized Additive Model(GAM)generally yielded less satisfactory prediction accuracy compared to the other methods.展开更多
Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193...Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz.One part of the 1030-nm laser from the homemade Yb:YAG crystal amplifier is divided to generate 258 nm laser(1.2 W)by fourth-harmonic generation,and the rest is used to pump an optical parametric amplifier producing 1553 nm laser(700 mW).Frequency mixing of these beams in cascaded LiB_(3)O_(5) crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz.By introducing a spiral phase plate to the 1553-nm beam before frequency mixing,we generate a vortex beam carrying orbital angular momentum.This is,to our knowledge,the first demonstration of a 193-nm vortex beam generated from a solid-state laser.Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection.展开更多
A coherent mid-infrared laser source,which can be tuned from 7.2 μm to 12.2 μm based on the type-Ⅰ phase-matched difference frequency generation(DFG) in an uncoated ZnGeP2(ZGP) crystal,is reported.The two pump wave...A coherent mid-infrared laser source,which can be tuned from 7.2 μm to 12.2 μm based on the type-Ⅰ phase-matched difference frequency generation(DFG) in an uncoated ZnGeP2(ZGP) crystal,is reported.The two pump waves are from a type-Ⅱ phase-matched dual-wavelength KTP optical parametric oscillator(OPO) of which the signal and idler waves are tuned during 1.85-1.96 μm(extraordinary wave) and 2.5-2.33 μm(ordinary wave),respectively.The maximum energy of the generated mid-infrared laser is 10 μJ at 9.22 μm,corresponding to the peak power of 2.2 kW.展开更多
The energy levels, wave functions and the second-order nonlinear susceptibilities are calculated in GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As asymmetric quantum well （AQW） by using an asymmetric model based on the parabolic an...The energy levels, wave functions and the second-order nonlinear susceptibilities are calculated in GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As asymmetric quantum well （AQW） by using an asymmetric model based on the parabolic and non-parabolic band. The influence of non-parabolicity can not be neglected when analyzing the phenomena in narrow quantum wells and in higher lying subband edges in wider wells. The numerical results show that under double resonance （DR） conditions, the second- order difference frequency generation （DFG） and optical rectification （OR） generation susceptibilities in the AQW reach 2.5019 μm/V and 13.208 μm/V, respectively, which are much larger than those of the bulk GaAs. Besides, we calculate the absorption coefficient of AQW and find out the two pump wavelengths correspond to the maximum absorption, so appropriate pump beams must be selected to generate terahertz （THz） radiation by DFG.展开更多
This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of a...This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.展开更多
We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cav- ities with an input tripartite entangled state at fundamental frequency. The entanglement properties of ...We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cav- ities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the trans- naission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network.展开更多
An all-optical format conversion from non-return-to-zero （NRZ） to return-to-zero （RZ） is presented based on cross-phase modulation （XPM） in a silicon waveguide with a detuned optical bandpass filter （OBPF）. Th...An all-optical format conversion from non-return-to-zero （NRZ） to return-to-zero （RZ） is presented based on cross-phase modulation （XPM） in a silicon waveguide with a detuned optical bandpass filter （OBPF）. The simulation results show that the tunable bandwidth of the OBPF leads.to RZ signals with tunable pulse width. The conversion efficiency （CE） and the pattern effect of the RZ signal are attributed to the parameters of the pump pulse and the OBPE The converted RZ signal exhibits lower timing jitter than the NRZ signal.展开更多
The cryogenic hydraulic turbine can be used to replace the conventional JeT valve for LNG or mixed refrigerant throttling and depressurization in a natural gas liquefaction plant.This advanced technology is not only t...The cryogenic hydraulic turbine can be used to replace the conventional JeT valve for LNG or mixed refrigerant throttling and depressurization in a natural gas liquefaction plant.This advanced technology is not only to enhance the efficiency of the liquefaction plant,but to usher a new trend in the development of global liquefaction technologies.China has over 136 liquefaction plants,but the cryogenic hydraulic turbines have not been deployed in industrial utilization.In addition,these turbines cannot be manufactured domestically.In this circumstance,through working on the key technologies for LNG hydraulic turbine process&control system development,hydraulic model optimization design,structure design and manufacturing,the first domestic cryogenic hydraulic turbine with a flow rate of 40 m^(3)/h was developed to recover the pressure energy from the LNG of cold box.The turbine was installed in the CNOOC Zhuhai Natural Gas Liquefaction Plant for industrial tests under multiple working conditions,including start-stop,variable flow rates and variable rotation speeds.Test results show that the domestic LNG cryogenic hydraulic turbine has satisfactory mechanical and operational performances at low temperatures as specified in design.In addition,the process&control system and frequency-conversion power-generation system of the turbine system are designed properly to automatically and smoothly replace the existing LNG JeT valve.As a result,the domestic LNG cryogenic hydraulic turbine system can improve LNG production by an average of 2%and generate power of 8.3 kW.展开更多
In the process of the continuous development of power electronics technology, motor control gradually toward more optimized, efficient direction. In this paper, the variable frequency asynchronous motor control system...In the process of the continuous development of power electronics technology, motor control gradually toward more optimized, efficient direction. In this paper, the variable frequency asynchronous motor control system as the research object, mainly discusses the design requirements and design content of PLC in the variable frequency asynchronous motor control system, to achieve the control effect of the motor.展开更多
Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructure...Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructured nonlinear crystals like periodic-poled lithium niobate(PPLN)crystals.In this paper,we propose and show that the incident angle of pump laser light can be harnessed as an alternative versatile tool to engineer QPM for high-efficiency SHG in a PPLN crystal,in addition to conventional means of period adjusting or temperature tuning.A rigorous model is established and analytical solution of the nonlinear conversion efficiency under the small and large signal approximation theory is obtained at different incident angles.The variation of phase mismatching and walk-off length with incident angle or incident wavelength are also explored.Numerical simulations for a PPLN crystal with first order QPM structure are used to confirm our theoretical predictions based on the exact analytical solution of the general large-signal theory.The results show that the narrow-band tunable SHG output covers a range of 532 nm–552.8 nm at the ideal incident angle from 0°to 90°.This theoretical scheme,fully considering the reflection and transmission at the air-crystal interface,would offer an efficient theoretical system to evaluate the nonlinear frequency conversion and help to obtain the maximum SHG conversion efficiency by selecting an optimum incident wavelength and incident angle in a specially designed PPLN crystal,which would be very helpful for the design of tunable narrow-band pulse nanosecond,picosecond,and femtosecond laser devices via PPLN and other microstructured LN crystals.展开更多
基金funded by the National Natural Science Foundation of China(42174131).
文摘Characterizing the petrophysical properties holds significant importance in shale oil reservoirs.Twodimensional(2-D)nuclear magnetic resonance(NMR),a nondestructive and noninvasive technique,has numerous applications in petrophysical characterization.However,the complex occurrence states of the fluids and the highly non-uniform distributions of minerals and organic matter pose challenges in the NMR-based petrophysical characterization.A novel T_(1)-T_(2)relaxation theory is introduced for the first time in this study.The transverse and longitudinal relaxivities of pore fluids are determined based on numerical investigation and experimental analysis.Additionally,an improved random walk algorithm is proposed to,on the basis of digital shale core,simulate the effects of the hydrogen index(HI)for the organic matter,echo spacing(T_(E)),pyrite content,clay mineral type,and clay content on T_(1)-T_(2)spectra at different NMR frequencies.Furthermore,the frequency conversion cross-plots for various petrophysical parameters influenced by the above factors are established.This study provides new insights into NMRbased petrophysical characterization and the frequency conversion of petrophysical parameters measured by laboratory NMR instruments and NMR logging in shale oil reservoirs.It is of great significance for the efficient exploration and environmentally friendly production of shale oil.
基金Science and Technology Project of Aerospace Information Research Institute,Chinese Academy of Sciences(Y910340Z2F)Science and Technology Project of BBEF(E3E2010201)。
文摘Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting their potential applications.Therefore,it is imperative to study the creation of lowfrequency signals using antennas with suitable dimensions.In contrast to conventional mechanical antenna techniques,our study generates low-frequency signals in the spatial domain utilizing the principle of the Doppler effect.We also defines the antenna array architecture,the timing sequency,and the radiating element signal waveform,and provides experimental prototypes including 8/64 antennas based on earlier research.In the conducted experiments,121 MHz,40 MHz,and 10 kHz composite signals are generated by 156 MHz radiating element signals.The composite signal spectrum matches the simulations,proving our low-frequency signal generating method works.This holds significant implications for research on generating low-frequency signals with small-sized antennas.
基金Supported by the Anhui Provincial Natural Science Foundation under Grant No 1608085MA09the National Natural Science Foundation of China under Grant Nos 11774262,61675006,11474003 and 61472282
文摘The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the real-space Hamiltonian. The calculated results show that the probability of single photon frequency down-or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling.We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon. The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown. Our results may be useful in designing quantum devices at the single-photon level.
文摘The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-band is realized by combining with the local oscillator and the power control circuit to complete functions such as amplification, filtering and gain. In order to achieve the performance optimization and a high level of integration of the Ku-band monolithic microwave integrated circuits(MMIC) operating chip, the 3 D vertical interconnection micro-assembly technology is used. By stacking solder balls on the printed circuit board(PCB), the technology decreases the volume of the original transceiver to a miniaturized module. The module has a good electromagnetic compatibility through special structure designs. This module has the characteristics of miniaturization, low power consumption and high density, which is suitable for popularization in practical application.
基金supported by the Air Force Offce of Scientific Research(AFOSR)Multidisciplinary University Research Initiative(MURI)award on Novel light-matter interactions in topologically non-trivial Weyl semimetal structures and systems(award No.FA9550-20-1-0322)AFOSR MURI award on Programmable systems with non-Hermitian quantum dynamics(award no.FA9550-21-1-0202)+5 种基金ONR MURI award on the classical entanglement of light(award No.N00014-20-1-2789)the Army Research Offce(W911NF-23-1-0312)the Department of Energy(DE-SCo022282)W.M.Keck Foundation,the Department of Energy(DE-SCo025224),MPS Simons collaboration(Simons grant No.733682)US Air Force Research Laboratory(FA86511820019)AFRL-Applied Research Solutions(S03015)(FA8650-19-C-1692).
文摘Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global conversion efficiencies in such nonlinear environments has long been considered impossible,here,we formally address this challenge even in scenarios involving a very large number of spatial modes.By utilizing fundamental notions from optical statistical mechanics,we develop a universal theoretical framework that effectively treats all frequency components as chemical reactants/products,capable of undergoing optical thermodynamic reactions facilitated by a variety of multi-wave mixing effects.These photon-photon reactions are governed by conservation laws that directly determine the optical temperatures and chemical potentials of the ensued chemical equilibria for each frequency species.In this context,we develop a comprehensive stoichiometric model and formally derive an expression that relates the chemical potentials to the optical stoichiometric coefficients,in a manner akin to atomic/molecular chemical reactions.This advancement unlocks new predictive capabilities that can facilitate the optimization of frequency generation in highly multimode photonic arrangements,surpassing the limitations of conventional schemes that rely exclusively on nonlinear optical dynamics.Notably,we identify a universal regime of Rayleigh-Jeans thermalization where an optical reaction at near-zero optical temperatures can promote the complete and entropically irreversible conversion of light to the fundamental mode at a target frequency.Our theoretical results are corroborated by numerical simulations in settings where second-harmonic generation,sum-frequency generation and four-wave mixing processes can manifest.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB921603)the National Natural Science Foundation of China(Grant Nos.11374126,11347137,11404336,and 11204103)+1 种基金the China Postdoctoral Science Foundation(Grant No.2013T60317)the National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)
文摘We experimentally demonstrate multiple frequency conversion via atomic spin coherence of storing a light pulse in a doped solid. The essence of this multiple frequency conversion is four-wave mixing based on stored atomic spin coherence. Through electromagnetically induced transparency, an input probe pulse is stored into atomic spin coherence by modulating the intensity of the control field. By using two different control fields to interact with the coherently prepared medium, the stored atomic spin coherence can be transformed into three different information channels. Multiple frequency conversion is implemented efficiently by manipulating the spectra of the control fields to scatter atomic spin coherence. This multiple frequency conversion is expected to have potential applications in information processing and communication network.
基金supported by the National Natural Science Foundation of China (Grant No. 10974126)the National Basic Research Program of China (Grant No. 2010CB923102)
文摘In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-free frequency conversion of a quantum state can be achieved by injecting a strong signal field. The dependences of conversion efficiency on the pump parameter, extra losses and input state amplitude are also analysed.
文摘At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment control is becoming more and more obvious. Frequency conversion technology has the advantages of regulation and control, etc. The application of this technology in mines can promote the production efficiency of transportation and ventilation. Frequency conversion technology is widely used in modern life. Applying frequency conversion technology to mining equipment in modern coal mine mechanical and electrical engineering can ensure the smooth operation of mechanical and electrical equipment to a great extent. Therefore, this paper will focus on the application of frequency conversion technology in modern coal mine electromechanical engineering.
文摘The generation of optical vortices in compact systems and across different spectral regions can open new horizons for their applications in end-user devices.Latest advances in the design and fabrication of optical metasurfaces made of a quadratically nonlinear material enable highly precise creation of vortices with different topological charges at the second-harmonic frequency,with the potential to obtain various other structured states of light.
基金supported by the Israel Science Foundation through the MAPATS programby the US Air Force Office for Scientific Research,AFOSR.
文摘We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.
基金financially supported by Science and Technology Project of Quzhou(Grant Nos.2023K256,2023NC08)Research Grants Program of Department of Education of Zhejiang Province(No.Y202455709)+1 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LZY21E050001)University-Enterprise Cooperation Program for Visiting Engineers in Higher Education Institutions in Zhejiang Province(No.FG2020215).
文摘This paper investigates the start-up and shutdown phases of a five-bladed closed-impeller centrifugal pump through experimental analysis,capturing the temporal evolution of its hydraulic performances.The study also predicts the transient characteristics of the pump under non-rated operating conditions to assess the accuracy of various machine learning methods in forecasting its instantaneous performance.Results indicate that the pump’s transient behavior in power-frequency mode markedly differs from that in frequency-conversion mode.Specifically,the power-frequency mode achieves steady-state values faster and exhibits smaller fluctuations before stabilization compared to the other mode.During the start-up phase,as the steady-state flow rate increases,inlet and outlet pressures and head also rise,while torque and shaft power decrease,with rotational speed remaining largely unchanged.Conversely,during the shutdown phase,no significant changes were observed in torque,shaft power,or rotational speed.Six machine learning models,including Gaussian Process Regression(GPR),Decision Tree Regression(DTR),and Deep Learning Networks(DLN),demonstrated high accuracy in predicting the hydraulic performance of the centrifugal pump during the start-up and shutdown phases in both power-frequency and frequency-conversion conditions.The findings provide a theoretical foundation for improved prediction of pump hydraulic performance.For instance,when predicting head and flow rate during power-frequency start-up,GPR achieved absolute and relative errors of 0.54 m(7.84%)and 0.21 m3/h(13.57%),respectively,while the Feedforward Neural Network(FNN)reported errors of 0.98 m(8.24%)and 0.10 m3/h(16.71%).By contrast,the Support Vector Machine Regression(SVMR)and Generalized Additive Model(GAM)generally yielded less satisfactory prediction accuracy compared to the other methods.
基金supported by the Research Project of the Aerospace Information Research Institute,the Chinese Academy of Sciences(Grant Nos.E1Z1D101 and E2Z2D101)the Chinese Academy of Sciences(Grant No.E33310030D)the Guangzhou Basic and Applied Basic Research Foundation(Grant Nos.2023A04J0336 and 2023A04J0024).
文摘Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz.One part of the 1030-nm laser from the homemade Yb:YAG crystal amplifier is divided to generate 258 nm laser(1.2 W)by fourth-harmonic generation,and the rest is used to pump an optical parametric amplifier producing 1553 nm laser(700 mW).Frequency mixing of these beams in cascaded LiB_(3)O_(5) crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz.By introducing a spiral phase plate to the 1553-nm beam before frequency mixing,we generate a vortex beam carrying orbital angular momentum.This is,to our knowledge,the first demonstration of a 193-nm vortex beam generated from a solid-state laser.Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection.
基金supported by the Major State Basic Research Development Program of China (No. 2007CB310403)the National Natural Science Foundation of China (No. 60801017)Research Fund for the Doctoral Program of Higher Education (No. 20070420118)
文摘A coherent mid-infrared laser source,which can be tuned from 7.2 μm to 12.2 μm based on the type-Ⅰ phase-matched difference frequency generation(DFG) in an uncoated ZnGeP2(ZGP) crystal,is reported.The two pump waves are from a type-Ⅱ phase-matched dual-wavelength KTP optical parametric oscillator(OPO) of which the signal and idler waves are tuned during 1.85-1.96 μm(extraordinary wave) and 2.5-2.33 μm(ordinary wave),respectively.The maximum energy of the generated mid-infrared laser is 10 μJ at 9.22 μm,corresponding to the peak power of 2.2 kW.
基金supported by the National Basic Research Program of China (No.2007CB310403)the National Natural Science Foundation of China (Nos.60801017 and 61172010)the Science and Technology Committee of Tianjin (No.11JCYBJC01100)
文摘The energy levels, wave functions and the second-order nonlinear susceptibilities are calculated in GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As asymmetric quantum well （AQW） by using an asymmetric model based on the parabolic and non-parabolic band. The influence of non-parabolicity can not be neglected when analyzing the phenomena in narrow quantum wells and in higher lying subband edges in wider wells. The numerical results show that under double resonance （DR） conditions, the second- order difference frequency generation （DFG） and optical rectification （OR） generation susceptibilities in the AQW reach 2.5019 μm/V and 13.208 μm/V, respectively, which are much larger than those of the bulk GaAs. Besides, we calculate the absorption coefficient of AQW and find out the two pump wavelengths correspond to the maximum absorption, so appropriate pump beams must be selected to generate terahertz （THz） radiation by DFG.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB0806001)the Program for Changjiang and Innovative Research Team in UniversityShanghai Leading Academic Discipline Project (Grant No B408)
文摘This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.
基金Project supported by the National Natural Science Foundation of China(Grant No.91430109)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111401110004)the Natural Science Foundation of Shanxi Province,China(Grant No.2014011005-3)
文摘We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cav- ities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the trans- naission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network.
文摘An all-optical format conversion from non-return-to-zero （NRZ） to return-to-zero （RZ） is presented based on cross-phase modulation （XPM） in a silicon waveguide with a detuned optical bandpass filter （OBPF）. The simulation results show that the tunable bandwidth of the OBPF leads.to RZ signals with tunable pulse width. The conversion efficiency （CE） and the pattern effect of the RZ signal are attributed to the parameters of the pump pulse and the OBPE The converted RZ signal exhibits lower timing jitter than the NRZ signal.
文摘The cryogenic hydraulic turbine can be used to replace the conventional JeT valve for LNG or mixed refrigerant throttling and depressurization in a natural gas liquefaction plant.This advanced technology is not only to enhance the efficiency of the liquefaction plant,but to usher a new trend in the development of global liquefaction technologies.China has over 136 liquefaction plants,but the cryogenic hydraulic turbines have not been deployed in industrial utilization.In addition,these turbines cannot be manufactured domestically.In this circumstance,through working on the key technologies for LNG hydraulic turbine process&control system development,hydraulic model optimization design,structure design and manufacturing,the first domestic cryogenic hydraulic turbine with a flow rate of 40 m^(3)/h was developed to recover the pressure energy from the LNG of cold box.The turbine was installed in the CNOOC Zhuhai Natural Gas Liquefaction Plant for industrial tests under multiple working conditions,including start-stop,variable flow rates and variable rotation speeds.Test results show that the domestic LNG cryogenic hydraulic turbine has satisfactory mechanical and operational performances at low temperatures as specified in design.In addition,the process&control system and frequency-conversion power-generation system of the turbine system are designed properly to automatically and smoothly replace the existing LNG JeT valve.As a result,the domestic LNG cryogenic hydraulic turbine system can improve LNG production by an average of 2%and generate power of 8.3 kW.
文摘In the process of the continuous development of power electronics technology, motor control gradually toward more optimized, efficient direction. In this paper, the variable frequency asynchronous motor control system as the research object, mainly discusses the design requirements and design content of PLC in the variable frequency asynchronous motor control system, to achieve the control effect of the motor.
基金Project supported by the National Natural Science Foundation of China(Grant No.11974119)the Science and Technology Project of Guangdong Province,China(Grant No.2020B010190001)+2 种基金the Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06C594)the National Key Research and Development Program of China(Grant Nos.2018YFA,0306200,and 2019YFB2203500)the Science and Technology Program of Guangzhou City(Grant No.2023A04J1309).
文摘Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructured nonlinear crystals like periodic-poled lithium niobate(PPLN)crystals.In this paper,we propose and show that the incident angle of pump laser light can be harnessed as an alternative versatile tool to engineer QPM for high-efficiency SHG in a PPLN crystal,in addition to conventional means of period adjusting or temperature tuning.A rigorous model is established and analytical solution of the nonlinear conversion efficiency under the small and large signal approximation theory is obtained at different incident angles.The variation of phase mismatching and walk-off length with incident angle or incident wavelength are also explored.Numerical simulations for a PPLN crystal with first order QPM structure are used to confirm our theoretical predictions based on the exact analytical solution of the general large-signal theory.The results show that the narrow-band tunable SHG output covers a range of 532 nm–552.8 nm at the ideal incident angle from 0°to 90°.This theoretical scheme,fully considering the reflection and transmission at the air-crystal interface,would offer an efficient theoretical system to evaluate the nonlinear frequency conversion and help to obtain the maximum SHG conversion efficiency by selecting an optimum incident wavelength and incident angle in a specially designed PPLN crystal,which would be very helpful for the design of tunable narrow-band pulse nanosecond,picosecond,and femtosecond laser devices via PPLN and other microstructured LN crystals.
