In underdense plasmas, the transverse ponderomotive force of an intense laser beam with Ganssian transverse profile expels electrons radially, and it can lead to an electron cavitstion. An improved cavitation model wi...In underdense plasmas, the transverse ponderomotive force of an intense laser beam with Ganssian transverse profile expels electrons radially, and it can lead to an electron cavitstion. An improved cavitation model with charge conservation constraint is applied to the determination of the width of the electron cavity. The envelope equation for spot size derived by using source-dependent expansion method is extended to including the electron cavity. The condition for self-guiding is given and illuminated by an effective potential for the laser spot size. The effects of the laser power, plasma density and energy dissipation on the self-guiding condition are discussed.展开更多
The deployment of mega constellations has had a significant effect on the compounding space debris environment,increasing the number of on-orbit objects in all conditions and damaging the stability of the space debris...The deployment of mega constellations has had a significant effect on the compounding space debris environment,increasing the number of on-orbit objects in all conditions and damaging the stability of the space debris environment.The increased density of space objects is associated with an increased risk of on-orbit collisions.Collision risk exists not only between a mega constellation and the space debris environment but also inside a mega constellation.In this study,we used the Starlink constellation to investigate the self-induced collision risk caused by malfunctioning satellites.First,we analyzed the conjunction condition between malfunctioning and operative satellites based on long-term orbital evolution characteristics.The collision probability was then calculated based on the conjunction analysis results.The results show that malfunctioning satellites in Phase 1 cause an 86.2%self-induced collision probability based on a malfunctioning rate of 1%,which is close to the collision probability caused by objects larger than 6 cm during five years of service.Therefore,self-induced collisions are another important risk factor for the Starlink constellation.展开更多
Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provi...Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provided that the initial map u0 is in a suitable nontrivial homotopy class with energy small enough.展开更多
Transparency and perfect absorption are two contradictory terms;a perfect absorber never permits waves to transmit through.However,this statement only remains true in the linear regime,where the nonlinearity has been ...Transparency and perfect absorption are two contradictory terms;a perfect absorber never permits waves to transmit through.However,this statement only remains true in the linear regime,where the nonlinearity has been omitted and the physical system like the perfect absorber is not affected by the incoming waves.Here we experimentally demonstrate an intriguing self-induced transparency effect in a perfectly absorbing optical microcavity,which perfectly absorbs any incoming waves at the low power level,but allows a portion of waves to be transmitted at the higher power due to the nonlinear coupling between the fundamental and its second harmonic modes.Moreover,the asymmetric scattering nature of the microcavity enables a chiral and unidirectional reflection in one of the input ports,this leads to asymmetric and chiral coherent control of the perfect absorption states through phase varying.More importantly,such chiral behaviors also empower the chiral emission of second-harmonic generation with a high distinct ratio in the transparency state.These results pave the way for controllable transparency in a wide range of fields in optics,microwaves,acoustics,mechanics,and matter waves.展开更多
We investigate the shape-preserving propagation of N optical pulses in an （N ＋ 1）-level medium. We solve Maxwell-Schroedinger equations exactly and provide several types of explicit coupled soliton solutions, which...We investigate the shape-preserving propagation of N optical pulses in an （N ＋ 1）-level medium. We solve Maxwell-Schroedinger equations exactly and provide several types of explicit coupled soliton solutions, which are temporally amplitude- and group-velocity-matched multi-mode slow-optical pulses of the system.展开更多
White-light continuum can be induced by the interaction of intense femtosecond laser pulses with condensed materials.By using two orthogonal polarizers,a self-induced birefringence of continuum is observed when focusi...White-light continuum can be induced by the interaction of intense femtosecond laser pulses with condensed materials.By using two orthogonal polarizers,a self-induced birefringence of continuum is observed when focusing femtosecond laser pulses into bulk fused silica.That is,the generated white-light continuum is synchronously modulated anisotropically while propagating in fused silica.Time-resolved detection confirms that self-induced birefringence of continuum shows a growth and saturation feature with time evolution.By adjusting laser energy,the transmitted intensity of continuum modulated by self-induced birefringence also varies correspondingly.Morphology analysis with time evolution indicates that it is the focused femtosecond laser pulses that induce anisotropic microstructures in bulk fused silica,and the anisotropic structures at the same time modulate the generated continuum.展开更多
The self-induced unsteadiness in tip leakage flow(TLF)of a micro-axial fan rotor is numerically studied by solving Reynolds-averaged Navier-Stokes equations.The micro-axial fan,which is widely used in cooling systems ...The self-induced unsteadiness in tip leakage flow(TLF)of a micro-axial fan rotor is numerically studied by solving Reynolds-averaged Navier-Stokes equations.The micro-axial fan,which is widely used in cooling systems of electronic devices,has a tip clearance of 6%of the axial chord length of the blade.At the design rotation speed,four cases near the peak efficiency point(PEP)with self-induced unsteadiness and four steady cases which have much weaker pressure fluctuations are investigated.Using the"interface"separating the incoming main flow and the TLF defined by Duet al.[1],an explanation based on the propagation of the low energy spot and its multi-passing through the high gradient zone of the relative total pressure,is proposed to clarify the originating mechanism of the unsteadiness.At the operating points near the PEP,the main flow is weaker than the TLF and the interface moves upstream.The low energy spot which propagates along in the close behind of the interface has opportunity to circulate in the circumferential direction and passes through the sensitive interfaces several times,a slight perturbation therefore may be magnified significantly and develops into the self-induced unsteadiness.The explanation is demonstrated by numerical results.展开更多
We theoretically investigate the propagation of few-cycle laser pulses in resonant two-level dense media with a sub- wavelength structure, which is described by the full Maxwell-Bloch equations without the frame of sl...We theoretically investigate the propagation of few-cycle laser pulses in resonant two-level dense media with a sub- wavelength structure, which is described by the full Maxwell-Bloch equations without the frame of slowly varying envelope and rotating wave approximations. The input pulses can be shaped into shorter ones with a single or less than one optical cycle. The effect of the parameters of the subwavelength structure and laser pulses is studied. Our study shows that the media with a subwavelength structure can significantly shape the few-cycle pulses into a subcycle pulse, even for the case of chirp pulses as input fields. This suggests that such subwavelength structures have potential application in the shaping of few-cycle laser pulses.展开更多
We derive an N-fold Darboux transformation for the nonlinear Schrdinger equation coupled to a multiple selfinduced transparency system, which is applicable to optical fiber communications in the erbium-doped medium.Th...We derive an N-fold Darboux transformation for the nonlinear Schrdinger equation coupled to a multiple selfinduced transparency system, which is applicable to optical fiber communications in the erbium-doped medium.The N-soliton, N-breather and N th-order rogue wave solutions in the compact determinant representations are derived using the Darboux transformation and limit technique. Dynamics of such solutions from the first-to second-order ones are shown.展开更多
In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injec...In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injection with self-induced current, which does not require electrodes. The improved analytical model is derived to evaluate the electron density reduction taking into consideration the self-induced current for various TMF velocities. The plasma reduction performance is analyzed for several conditions including the total absence of injected current. The results show that the velocity may be used to trade off the injected current and, when sufficiently large, eliminates the need for an injected current while mitigating radio blackout. The effectiveness of this solution to the blackout problem is demonstrated in commonly used aerospace communication bands. With a field strength of less than 0.15 T, increasing the velocity from40 m s^-1 to 3100 m s^-1 is all that is required to obviate the need for an injected current. Moreover,typical reduction ratios for electronic density tolerance(2, 1.9, 1.75 and 3 times for the L-, S-, Cand X-bands, respectively, at an altitude of 40 km) remain unchanged. Increasing the velocity of the TMF is much easier than injecting current via a metal electrode into a high-temperature flow field. The TMF method appears practical in regard to possible future applications.展开更多
The laws of formation of the impulse of electromagnetic radiation in dielectric environment for conditions self-induced transparency are considered. The insufficiency of the description of such impulse with the help o...The laws of formation of the impulse of electromagnetic radiation in dielectric environment for conditions self-induced transparency are considered. The insufficiency of the description of such impulse with the help of the equations Maxwell-Bloch is shown. The way of connection of an average number filling and energy of the impulse taking into account energy saturation of environment are offered. The calculation of an electrical component of the impulse is submitted.展开更多
Optical traps have emerged as powerful tools for immobilizing and manipulating small particles in three dimensions.Fiber-based optical traps(FOTs)significantly simplify optical setup by creating trapping centers with ...Optical traps have emerged as powerful tools for immobilizing and manipulating small particles in three dimensions.Fiber-based optical traps(FOTs)significantly simplify optical setup by creating trapping centers with single or multiple pieces of optical fibers.In addition,they inherit the flexibility and robustness of fiber-optic systems.However,trapping 10-nm-diameter nanoparticles(NPs)using FOTs remains challenging.In this study,we model a coaxial waveguide that works in the optical regime and supports a transverse electromagnetic(TEM)-like mode for NP trapping.Single NPs at waveguide front-end break the symmetry of TEM-like guided mode and lead to high transmission efficiency at far-field,thereby strongly altering light momentum and inducing a large-scale back-action on the particle.We demonstrate,via finite-difference time-domain(FDTD)simulations,that this FOT allows for trapping single 10-nm-diameter NPs at low power.展开更多
The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equatio...The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guides through cascading x(2) effect called self-induced soliton wave-guide. Transverse refractive index distribution of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process. Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Because the power needed for forming the spatial solitons in cascading process is much lower than that in Kerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signal process.展开更多
基金Project supported by the National High Technology Inertial Confinement Fusion Foundation （Grant No 10335020/A0506）, the National Natural Science Foundation of China （Grant Nce 10474081 and 10576035）, and Natural Science Foundation of Shanghai （Grant No 05ZR14159）.
文摘In underdense plasmas, the transverse ponderomotive force of an intense laser beam with Ganssian transverse profile expels electrons radially, and it can lead to an electron cavitstion. An improved cavitation model with charge conservation constraint is applied to the determination of the width of the electron cavity. The envelope equation for spot size derived by using source-dependent expansion method is extended to including the electron cavity. The condition for self-guiding is given and illuminated by an effective potential for the laser spot size. The effects of the laser power, plasma density and energy dissipation on the self-guiding condition are discussed.
文摘The deployment of mega constellations has had a significant effect on the compounding space debris environment,increasing the number of on-orbit objects in all conditions and damaging the stability of the space debris environment.The increased density of space objects is associated with an increased risk of on-orbit collisions.Collision risk exists not only between a mega constellation and the space debris environment but also inside a mega constellation.In this study,we used the Starlink constellation to investigate the self-induced collision risk caused by malfunctioning satellites.First,we analyzed the conjunction condition between malfunctioning and operative satellites based on long-term orbital evolution characteristics.The collision probability was then calculated based on the conjunction analysis results.The results show that malfunctioning satellites in Phase 1 cause an 86.2%self-induced collision probability based on a malfunctioning rate of 1%,which is close to the collision probability caused by objects larger than 6 cm during five years of service.Therefore,self-induced collisions are another important risk factor for the Starlink constellation.
基金supported partially by NSFC(Grant Nos.12141103 and 12301074)Guangzhou Basic and Applied Basic Research Foundation(Grant No.2024A04J3637)+1 种基金supported partially by NSFC(Grant No.11971400)National Key Research and Development Projects of China(Grant No.2020YFA0712500)。
文摘Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provided that the initial map u0 is in a suitable nontrivial homotopy class with energy small enough.
基金supported by the National Science Foundation of China(Grant No.92050113,No.12274295,No.11304201)National key research and development program(Grant No.2016YFA0302500,2017YFA0303700)Shanghai MEC Scientific Innovation Program(Grant No.E00075).
文摘Transparency and perfect absorption are two contradictory terms;a perfect absorber never permits waves to transmit through.However,this statement only remains true in the linear regime,where the nonlinearity has been omitted and the physical system like the perfect absorber is not affected by the incoming waves.Here we experimentally demonstrate an intriguing self-induced transparency effect in a perfectly absorbing optical microcavity,which perfectly absorbs any incoming waves at the low power level,but allows a portion of waves to be transmitted at the higher power due to the nonlinear coupling between the fundamental and its second harmonic modes.Moreover,the asymmetric scattering nature of the microcavity enables a chiral and unidirectional reflection in one of the input ports,this leads to asymmetric and chiral coherent control of the perfect absorption states through phase varying.More importantly,such chiral behaviors also empower the chiral emission of second-harmonic generation with a high distinct ratio in the transparency state.These results pave the way for controllable transparency in a wide range of fields in optics,microwaves,acoustics,mechanics,and matter waves.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10274021, 90403008, and 10434060, and the National Key Basic Research and Development Programme of China under Grant No 2005CB724508.
文摘We investigate the shape-preserving propagation of N optical pulses in an （N ＋ 1）-level medium. We solve Maxwell-Schroedinger equations exactly and provide several types of explicit coupled soliton solutions, which are temporally amplitude- and group-velocity-matched multi-mode slow-optical pulses of the system.
基金This research was supported by the National Key Research and Development Program of China(No.2016YFB1102402)the National Natural Science Foundation of China(No.61675214).
文摘White-light continuum can be induced by the interaction of intense femtosecond laser pulses with condensed materials.By using two orthogonal polarizers,a self-induced birefringence of continuum is observed when focusing femtosecond laser pulses into bulk fused silica.That is,the generated white-light continuum is synchronously modulated anisotropically while propagating in fused silica.Time-resolved detection confirms that self-induced birefringence of continuum shows a growth and saturation feature with time evolution.By adjusting laser energy,the transmitted intensity of continuum modulated by self-induced birefringence also varies correspondingly.Morphology analysis with time evolution indicates that it is the focused femtosecond laser pulses that induce anisotropic microstructures in bulk fused silica,and the anisotropic structures at the same time modulate the generated continuum.
基金funded by the National Natural Science Foundation of China under Grant 50876031by Shanghai Municipal Education Commission under Grant 10ZZ40
文摘The self-induced unsteadiness in tip leakage flow(TLF)of a micro-axial fan rotor is numerically studied by solving Reynolds-averaged Navier-Stokes equations.The micro-axial fan,which is widely used in cooling systems of electronic devices,has a tip clearance of 6%of the axial chord length of the blade.At the design rotation speed,four cases near the peak efficiency point(PEP)with self-induced unsteadiness and four steady cases which have much weaker pressure fluctuations are investigated.Using the"interface"separating the incoming main flow and the TLF defined by Duet al.[1],an explanation based on the propagation of the low energy spot and its multi-passing through the high gradient zone of the relative total pressure,is proposed to clarify the originating mechanism of the unsteadiness.At the operating points near the PEP,the main flow is weaker than the TLF and the interface moves upstream.The low energy spot which propagates along in the close behind of the interface has opportunity to circulate in the circumferential direction and passes through the sensitive interfaces several times,a slight perturbation therefore may be magnified significantly and develops into the self-induced unsteadiness.The explanation is demonstrated by numerical results.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61008016 and 61108006)the Natural Science Basis Research Plan in Shaanxi Province of China (Grant No. 2010JQ1002)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20106101120020)the Natural Science Foundation of Hubei Province, China (Grant No. 2011CDC155)
文摘We theoretically investigate the propagation of few-cycle laser pulses in resonant two-level dense media with a sub- wavelength structure, which is described by the full Maxwell-Bloch equations without the frame of slowly varying envelope and rotating wave approximations. The input pulses can be shaped into shorter ones with a single or less than one optical cycle. The effect of the parameters of the subwavelength structure and laser pulses is studied. Our study shows that the media with a subwavelength structure can significantly shape the few-cycle pulses into a subcycle pulse, even for the case of chirp pulses as input fields. This suggests that such subwavelength structures have potential application in the shaping of few-cycle laser pulses.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11705290 and 11305060the China Postdoctoral Science Foundation under Grant No 2016M602252
文摘We derive an N-fold Darboux transformation for the nonlinear Schrdinger equation coupled to a multiple selfinduced transparency system, which is applicable to optical fiber communications in the erbium-doped medium.The N-soliton, N-breather and N th-order rogue wave solutions in the compact determinant representations are derived using the Darboux transformation and limit technique. Dynamics of such solutions from the first-to second-order ones are shown.
基金supported by National Natural Science Foundation of China(Nos.61771370,61701381,and 11704296)。
文摘In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injection with self-induced current, which does not require electrodes. The improved analytical model is derived to evaluate the electron density reduction taking into consideration the self-induced current for various TMF velocities. The plasma reduction performance is analyzed for several conditions including the total absence of injected current. The results show that the velocity may be used to trade off the injected current and, when sufficiently large, eliminates the need for an injected current while mitigating radio blackout. The effectiveness of this solution to the blackout problem is demonstrated in commonly used aerospace communication bands. With a field strength of less than 0.15 T, increasing the velocity from40 m s^-1 to 3100 m s^-1 is all that is required to obviate the need for an injected current. Moreover,typical reduction ratios for electronic density tolerance(2, 1.9, 1.75 and 3 times for the L-, S-, Cand X-bands, respectively, at an altitude of 40 km) remain unchanged. Increasing the velocity of the TMF is much easier than injecting current via a metal electrode into a high-temperature flow field. The TMF method appears practical in regard to possible future applications.
文摘The laws of formation of the impulse of electromagnetic radiation in dielectric environment for conditions self-induced transparency are considered. The insufficiency of the description of such impulse with the help of the equations Maxwell-Bloch is shown. The way of connection of an average number filling and energy of the impulse taking into account energy saturation of environment are offered. The calculation of an electrical component of the impulse is submitted.
基金the National Natural Science Foundation of China(Grant No.11874164)the Innovation Fund of Wuhan National Laboratory for Optoelectronics and 1000 Talent Youth Program.The authors declare no conflicts of interest.
文摘Optical traps have emerged as powerful tools for immobilizing and manipulating small particles in three dimensions.Fiber-based optical traps(FOTs)significantly simplify optical setup by creating trapping centers with single or multiple pieces of optical fibers.In addition,they inherit the flexibility and robustness of fiber-optic systems.However,trapping 10-nm-diameter nanoparticles(NPs)using FOTs remains challenging.In this study,we model a coaxial waveguide that works in the optical regime and supports a transverse electromagnetic(TEM)-like mode for NP trapping.Single NPs at waveguide front-end break the symmetry of TEM-like guided mode and lead to high transmission efficiency at far-field,thereby strongly altering light momentum and inducing a large-scale back-action on the particle.We demonstrate,via finite-difference time-domain(FDTD)simulations,that this FOT allows for trapping single 10-nm-diameter NPs at low power.
文摘The formation of the spatial solitons in the quadratic nonlinearity x(2) media by cascading second harmonic generation (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodinger equation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guides through cascading x(2) effect called self-induced soliton wave-guide. Transverse refractive index distribution of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process. Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Because the power needed for forming the spatial solitons in cascading process is much lower than that in Kerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signal process.
