Here a new scheme for mode filtering is proposed. Based on the ponderomotive force effect,propagation of the microwave dual-mode through a plasma-filled metallic rectangular waveguide is investigated. To excite the TE...Here a new scheme for mode filtering is proposed. Based on the ponderomotive force effect,propagation of the microwave dual-mode through a plasma-filled metallic rectangular waveguide is investigated. To excite the TE_（20） mode in a rectangular waveguide, the existence of fundamental modes is unavoidable. To filter the destructive mode（TE_（10））, the waveguide is filled with a collisional plasma. Based on the coupling effect, the energy of this destructive TE_（10） mode is transferred to the TE_（20） mode. The proposed structure acts like a mode convertor. The TE_（10） mode become more attenuated and instead the TE_（20） mode is amplified. The plasma filled rectangular waveguide acts as a mode filtering tool.展开更多
In this paper, the growth rate, ponderomotive force and the exciting condition for parametric instability are derived by considering the loss reaction using a new method. On the basis of the hydrodynamic equations, we...In this paper, the growth rate, ponderomotive force and the exciting condition for parametric instability are derived by considering the loss reaction using a new method. On the basis of the hydrodynamic equations, we take the production and loss reactions in plasma into account to derive the coupling equations for the electron plasma oscillation and ion acoustic oscillation, and obtain the growth rate for the parametric instability, the ponderomotive force and the exciting condition. The result shows that （a） the production reaction has no effect on the parametric instability, and the effect of loss reaction on the parametric instability is a damping one, （b） the more intensive the external field or pump is, the larger the growth rate is, （c） there exist two modes of the ponderomotive force, i.e. the high frequency mode and the low frequency mode, and （d） when ponderomotive force counteracts the damping force, the oscillations become non-damping and non-driving. The ratio of the electron plasma oscillation to ion acoustic oscillation is independent of the loss reaction and the external field.展开更多
A fundamental difference of very high intensity laser interaction with plasmas from solid targets appears with lasing at picosecond （ps） pulse durations in contrast to pulses of nanosec-onds （ns）. This can be seen...A fundamental difference of very high intensity laser interaction with plasmas from solid targets appears with lasing at picosecond （ps） pulse durations in contrast to pulses of nanosec-onds （ns）. This can be seen from the more than 10,000 times higher acceleration with ps pulse du-rations than with thermal pressure determined interaction. A ps pulse duration produces instantly acting high-efficiency nonlinear （ponderomotive） electrodynamic force dominated acceleration in contrast to heating with longer pulses. The ps pulses accelerate high-density plasma blocks. This can be used by a new scheme of side-on driven laser fusion with generating a flame ignition in uncompressed fusion fuel of solid density resulting in a reaction velocity of more than 2000 km/s for DT.展开更多
Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the gover...Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the governing equations can be derived from this principle. Illustrational examples are given.展开更多
Based on the covariant Lagrangian function and Euler-Lagrange equation,a set of classical fluid equations for strong EM wave-spin plasma interaction is derived.Analysis shows that the relativistic effects may affect t...Based on the covariant Lagrangian function and Euler-Lagrange equation,a set of classical fluid equations for strong EM wave-spin plasma interaction is derived.Analysis shows that the relativistic effects may affect the interaction processes by three factors:the relativistic factor,the time component of four-spin,and the velocity-field coupling.This set of equations can be used to discuss the collective spin effects of relativistic electrons in classical regime,such as astrophysics,high-energy laser-plasma systems and so on.As an example,the spin induced ponderomotive force in the interaction of strong EM wave and magnetized plasma is investigated.Results show that the time component of four-spin,which approaches to zero in nonrelativistic situations,can increase the spin-ponderomotive force obviously in relativistic situation.展开更多
The interactions of laser field with plasma are studied by using the analog model of gravity. The interactions of laser field with plasma are regarded as an equivalent effective geometry. An effective metric for a pla...The interactions of laser field with plasma are studied by using the analog model of gravity. The interactions of laser field with plasma are regarded as an equivalent effective geometry. An effective metric for a plasma electron is developed. Validity of the metric is confirmed in the limit of non-relativity. The three-dimensional equation of motion for a plasma electron is derived from the general covariant equation of motion. The ponderomotive force and the Abraham＇s force are directly obtained from the three-dimensional equation.展开更多
A theoretical model was proposed to describe the effects of external bias electric field on terahertz(THz)generated in air plasma.The model predicted that for a plasma in a bias electric field,the amplification effect...A theoretical model was proposed to describe the effects of external bias electric field on terahertz(THz)generated in air plasma.The model predicted that for a plasma in a bias electric field,the amplification effect of the THz wave intensity increases with the increase of the excitation laser wavelength.We experimentally observed the relationship between the THz enhancement effect and the electric field strength at different wavelengths.Experimental results showed a good agreement with the model predictions.These results enhance our understanding of the physical mechanism by which femtosecond lasers excite air to generate THz and extend the practical applications of THz generation and modulation.展开更多
In this Letter,we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz(THz)wave emission from laser-ionized isotropic transparent dielectrics.Based on the laser energy a...In this Letter,we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz(THz)wave emission from laser-ionized isotropic transparent dielectrics.Based on the laser energy and incident angle dependences,we ascribe the THz emission to the ponderomotive force-induced dipole oscillation.Additionally,our investigation on the dependence of THz amplitude on the laser pulse duration confirms the dominant role of avalanche ionization in solid dielectrics.The THz emission can be utilized to indirectly monitor the ultrafast dynamics of carrier generation and motion during the laser ionization process of solid dielectrics.展开更多
Ultra-broadband,intense,coherent terahertz(THz)radiation can be generated,detected,and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector,with a frequency coverage spann...Ultra-broadband,intense,coherent terahertz(THz)radiation can be generated,detected,and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector,with a frequency coverage spanning across and beyond the whole THz gap."Such a research topic is termed plasma-based THz wave photonics in gas and liquid phases."In this paper,we review the most important experimental and theoretical works of the topic in the non-relativistic region with pump laser intensity below 1018 W/cm^(2).展开更多
The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low f...The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low field region in presence of a Cosh-Gaussian beam thereby producing density gradients in the transverse direction.The density gradients so produced the results in electron plasma wave(EPW)generation at the frequency of the input beam.The EPW interacts with the input beam resulting in the production of 2nd harmonics.WKB and paraxial approximations are employed for obtaining the 2nd order differential equation describing the behavior of the beam’s spot size against normalized distance.The impact of well-established laser-plasma parameters on the behavior of the beam’s spot size and SHG yield are also analyzed.The focusing behavior of the beam and SHG yield is enhanced with an increase in the density of plasma,the radius of the beam and the decentred parameter,and with a decrease in the intensity of the beam.The results of the current problem are really helpful for complete information of laser-plasma interaction physics.展开更多
This paper presents an investigation of self-focusing of a quadruple Gaussian laser beam in collisionless magnetized plasma.The nonlinearity due to ponderomotive force which arises on account of nonuniform intensity d...This paper presents an investigation of self-focusing of a quadruple Gaussian laser beam in collisionless magnetized plasma.The nonlinearity due to ponderomotive force which arises on account of nonuniform intensity distribution of the laser beam is considered.The nonlinear partial differential equation governing the evaluation of complex envelope in the slowly varying envelope approximation is solved using a paraxial formalism.The self-focusing mechanism in magnetized plasma,in the presence of self-compression mechanism will be analyzed in contrast to the case in which it is absent.It can be observed that,in case of ponderomotive nonlinearity,the self-compression mechanism obstructs the pulse self-focusing above a certain intensity value.The effect of an external magnetic field is to generate pulses with smaller spot size and shorter compression length.The lateral separation parameter and the initial intensity of the laser beam play a crucial role on focusing and compression parameters.Also,the three-dimensional analysis of pulse propagation is presented by coupling the self-focusing equation with the self-compression one.展开更多
This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma,in the presence of an external transverse field.Based on hydrodynamic equations,an...This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma,in the presence of an external transverse field.Based on hydrodynamic equations,an equation formulizing the parametric instability was derived.Furthermore,the formula for ponderomotive force and the expression that describes the electron acceleration were obtained.The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave.In addition,it can be concluded that ponderomotive force,due to the coupling of the external field(pump)to the Langmuir wave(ion-acoustic wave),is the driving force to excite the parametric instability and comprises the high-and low-frequency components.展开更多
基金supported by Hormoz branch, Islamic Azad University, Iran, Hormoze Island grant
文摘Here a new scheme for mode filtering is proposed. Based on the ponderomotive force effect,propagation of the microwave dual-mode through a plasma-filled metallic rectangular waveguide is investigated. To excite the TE_（20） mode in a rectangular waveguide, the existence of fundamental modes is unavoidable. To filter the destructive mode（TE_（10））, the waveguide is filled with a collisional plasma. Based on the coupling effect, the energy of this destructive TE_（10） mode is transferred to the TE_（20） mode. The proposed structure acts like a mode convertor. The TE_（10） mode become more attenuated and instead the TE_（20） mode is amplified. The plasma filled rectangular waveguide acts as a mode filtering tool.
基金Project supported by the National Natural Science Foundation of China （Grant No 40310223）, and the Fund of the National Key Laboratory of Electromagnetic Environment （Grant No 9140C080401060C0805）.
文摘In this paper, the growth rate, ponderomotive force and the exciting condition for parametric instability are derived by considering the loss reaction using a new method. On the basis of the hydrodynamic equations, we take the production and loss reactions in plasma into account to derive the coupling equations for the electron plasma oscillation and ion acoustic oscillation, and obtain the growth rate for the parametric instability, the ponderomotive force and the exciting condition. The result shows that （a） the production reaction has no effect on the parametric instability, and the effect of loss reaction on the parametric instability is a damping one, （b） the more intensive the external field or pump is, the larger the growth rate is, （c） there exist two modes of the ponderomotive force, i.e. the high frequency mode and the low frequency mode, and （d） when ponderomotive force counteracts the damping force, the oscillations become non-damping and non-driving. The ratio of the electron plasma oscillation to ion acoustic oscillation is independent of the loss reaction and the external field.
文摘A fundamental difference of very high intensity laser interaction with plasmas from solid targets appears with lasing at picosecond （ps） pulse durations in contrast to pulses of nanosec-onds （ns）. This can be seen from the more than 10,000 times higher acceleration with ps pulse du-rations than with thermal pressure determined interaction. A ps pulse duration produces instantly acting high-efficiency nonlinear （ponderomotive） electrodynamic force dominated acceleration in contrast to heating with longer pulses. The ps pulses accelerate high-density plasma blocks. This can be used by a new scheme of side-on driven laser fusion with generating a flame ignition in uncompressed fusion fuel of solid density resulting in a reaction velocity of more than 2000 km/s for DT.
基金Project supported by the National Natural Science Foundation of China(No.10472069).
文摘Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the governing equations can be derived from this principle. Illustrational examples are given.
基金supported by National Natural Science Foundation of China(No.12065011)Science and Technology Research Project of Jiangxi Provincial Department of Education(No.GJJ170642)。
文摘Based on the covariant Lagrangian function and Euler-Lagrange equation,a set of classical fluid equations for strong EM wave-spin plasma interaction is derived.Analysis shows that the relativistic effects may affect the interaction processes by three factors:the relativistic factor,the time component of four-spin,and the velocity-field coupling.This set of equations can be used to discuss the collective spin effects of relativistic electrons in classical regime,such as astrophysics,high-energy laser-plasma systems and so on.As an example,the spin induced ponderomotive force in the interaction of strong EM wave and magnetized plasma is investigated.Results show that the time component of four-spin,which approaches to zero in nonrelativistic situations,can increase the spin-ponderomotive force obviously in relativistic situation.
基金Project supported by the National Natural Science Foundation of China （Grant No.10573012）, the Shanghai Leading Aca- demic Discipline Project （Grant No.T0104）, and the Science Foundation of Shanghai Municipal Commission of Science and Technology （Grant No.07dz22020）
文摘The interactions of laser field with plasma are studied by using the analog model of gravity. The interactions of laser field with plasma are regarded as an equivalent effective geometry. An effective metric for a plasma electron is developed. Validity of the metric is confirmed in the limit of non-relativity. The three-dimensional equation of motion for a plasma electron is derived from the general covariant equation of motion. The ponderomotive force and the Abraham＇s force are directly obtained from the three-dimensional equation.
基金Natural Science Foundation of Beijing,China(Grant No.JQ18015),the National Natural Science Foundation of China(Grant Nos.61935001 and 61905271).
文摘A theoretical model was proposed to describe the effects of external bias electric field on terahertz(THz)generated in air plasma.The model predicted that for a plasma in a bias electric field,the amplification effect of the THz wave intensity increases with the increase of the excitation laser wavelength.We experimentally observed the relationship between the THz enhancement effect and the electric field strength at different wavelengths.Experimental results showed a good agreement with the model predictions.These results enhance our understanding of the physical mechanism by which femtosecond lasers excite air to generate THz and extend the practical applications of THz generation and modulation.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.62075157,62375199,and 62235013)the Tianjin Municipal Fund for Distinguished Young Scholars(No.20JCJQJC00190)the Key Fund of Shenzhen Natural Science Foundation(No.JCYJ20200109150212515)。
文摘In this Letter,we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz(THz)wave emission from laser-ionized isotropic transparent dielectrics.Based on the laser energy and incident angle dependences,we ascribe the THz emission to the ponderomotive force-induced dipole oscillation.Additionally,our investigation on the dependence of THz amplitude on the laser pulse duration confirms the dominant role of avalanche ionization in solid dielectrics.The THz emission can be utilized to indirectly monitor the ultrafast dynamics of carrier generation and motion during the laser ionization process of solid dielectrics.
基金supported by the National Natural Science Foundation of China(Nos.62075157,61875151,and 62235013)Tianjin Municipal Fund for Distinguished Young Scholars(No.20JCJQJC00190)+3 种基金Key Fund of Shenzhen Natural Science Foundation(No.JCYJ20200109150212515)National Key Research and Development Program of China(No.2017YFA0701000)Prof.Xi-Cheng Zhang in The Institute of Optics at University of Rochester has support from the Air Force Office of Scientific Research(Nos.FA9550-21-1-0389 and FA9550-21-1-0300)the National Science Foundation(No.ECCS-2152081).
文摘Ultra-broadband,intense,coherent terahertz(THz)radiation can be generated,detected,and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector,with a frequency coverage spanning across and beyond the whole THz gap."Such a research topic is termed plasma-based THz wave photonics in gas and liquid phases."In this paper,we review the most important experimental and theoretical works of the topic in the non-relativistic region with pump laser intensity below 1018 W/cm^(2).
文摘The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low field region in presence of a Cosh-Gaussian beam thereby producing density gradients in the transverse direction.The density gradients so produced the results in electron plasma wave(EPW)generation at the frequency of the input beam.The EPW interacts with the input beam resulting in the production of 2nd harmonics.WKB and paraxial approximations are employed for obtaining the 2nd order differential equation describing the behavior of the beam’s spot size against normalized distance.The impact of well-established laser-plasma parameters on the behavior of the beam’s spot size and SHG yield are also analyzed.The focusing behavior of the beam and SHG yield is enhanced with an increase in the density of plasma,the radius of the beam and the decentred parameter,and with a decrease in the intensity of the beam.The results of the current problem are really helpful for complete information of laser-plasma interaction physics.
文摘This paper presents an investigation of self-focusing of a quadruple Gaussian laser beam in collisionless magnetized plasma.The nonlinearity due to ponderomotive force which arises on account of nonuniform intensity distribution of the laser beam is considered.The nonlinear partial differential equation governing the evaluation of complex envelope in the slowly varying envelope approximation is solved using a paraxial formalism.The self-focusing mechanism in magnetized plasma,in the presence of self-compression mechanism will be analyzed in contrast to the case in which it is absent.It can be observed that,in case of ponderomotive nonlinearity,the self-compression mechanism obstructs the pulse self-focusing above a certain intensity value.The effect of an external magnetic field is to generate pulses with smaller spot size and shorter compression length.The lateral separation parameter and the initial intensity of the laser beam play a crucial role on focusing and compression parameters.Also,the three-dimensional analysis of pulse propagation is presented by coupling the self-focusing equation with the self-compression one.
基金supported by the National Natural Science Foundation of China (Grant No.40310223)the Fund of the National Key Laboratory of Electromagnetic Environment (No.9140C080401060C0805).
文摘This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma,in the presence of an external transverse field.Based on hydrodynamic equations,an equation formulizing the parametric instability was derived.Furthermore,the formula for ponderomotive force and the expression that describes the electron acceleration were obtained.The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave.In addition,it can be concluded that ponderomotive force,due to the coupling of the external field(pump)to the Langmuir wave(ion-acoustic wave),is the driving force to excite the parametric instability and comprises the high-and low-frequency components.
