The self-injection and acceleration of electrons in a hollow plasma channel driven by ultrashort intense laser pulses is investigated by Particle-in-Cell(PIC) simulations. It is shown that electrons from the bubble sh...The self-injection and acceleration of electrons in a hollow plasma channel driven by ultrashort intense laser pulses is investigated by Particle-in-Cell(PIC) simulations. It is shown that electrons from the bubble sheath will be self-injected into the hollow plasma channel and move radially towards the channel border due to the lack of focusing force in the hollow plasma channel. After several reflections near the channel wall by the strong focusing force, a self-injected electron bunch can be confined in the hollow plasma channel and quasi-phase-stably accelerated forward for the whole laser–plasma interaction process. These electrons using optical and plasma-related self-injection method can be self-organized to remain in the rear of the bubble, where the accelerating electric field is transversely uniform and nearly plateau along the propagation axis. Therefore, the self-injected electron bunch can be accelerated in a steady state without obvious oscillation and has a high quality with narrow energy spread and low divergence.展开更多
The nonlinear propagation of an intense Laguerre-Gaussian(LG)laser pulse in a parabolic preformed plasma channel is analyzed by means of the variational method.The evolution equation of the spot size is derived includ...The nonlinear propagation of an intense Laguerre-Gaussian(LG)laser pulse in a parabolic preformed plasma channel is analyzed by means of the variational method.The evolution equation of the spot size is derived including the effects of relativistic self-focusing,preformed channel focusing,and ponderomotive self-channeling.The parametric conditions of the LG laser pulse and plasma channel for propagating with constant spot size,periodically focusing and defocusing oscillation,catastrophic focusing,and solitary waves are obtained.Compared with the laser pulse with fundamental Gaussian(FG)mode,it is found that the effect of vacuum diffraction is reduced by half and the effects of relativistic and wakefield focusing are decreased by a quarter due to the hollow transverse intensity profile of the LG laser pulse,while the effect of channel focusing is the same order of magnitude with that of the FG laser pulse.Thus,the matched condition for the intense LG laser pulse with constant spot size is released obviously,while the parameters of the laser and plasma for the existence of solitary waves nearly coincide with those of the FG laser pulse.展开更多
The fluorescence from the out-of-focus region excited by the sidelobes of a Bessel beam is the major concern for light-sheet fluorescence microscopy （LSFM） with Bessel beam plane illumination. Here, we propose a met...The fluorescence from the out-of-focus region excited by the sidelobes of a Bessel beam is the major concern for light-sheet fluorescence microscopy （LSFM） with Bessel beam plane illumination. Here, we propose a method of applying the subtractive imaging to overcome the limitation of the conventional LSFM with Bessel beam plane illumination. In the proposed method, the sample is imaged twice by line scanning using the extended solid Bessel beam and the ring-like Bessel beam. By subtracting between the two images with similar out-of-focus blur, the improved image quality with the suppression of the Bessel beam sidelobes and enhanced sectioning ability with improved contrast are demonstrated.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11147005,61665006,and 61865011)the Natural Science Foundation of Jiangxi Province of China(Grant Nos.20151BAB202018,20161BAB212041,and 20162BCB23012)
文摘The self-injection and acceleration of electrons in a hollow plasma channel driven by ultrashort intense laser pulses is investigated by Particle-in-Cell(PIC) simulations. It is shown that electrons from the bubble sheath will be self-injected into the hollow plasma channel and move radially towards the channel border due to the lack of focusing force in the hollow plasma channel. After several reflections near the channel wall by the strong focusing force, a self-injected electron bunch can be confined in the hollow plasma channel and quasi-phase-stably accelerated forward for the whole laser–plasma interaction process. These electrons using optical and plasma-related self-injection method can be self-organized to remain in the rear of the bubble, where the accelerating electric field is transversely uniform and nearly plateau along the propagation axis. Therefore, the self-injected electron bunch can be accelerated in a steady state without obvious oscillation and has a high quality with narrow energy spread and low divergence.
基金the National Natural Science Foundation of China(Grant Nos.61665006 and 61865011)the Natural Science Foundation of Jiangxi Province of China(Grant Nos.20171ACB21018,20161BAB212041,and 20162BCB23012).
文摘The nonlinear propagation of an intense Laguerre-Gaussian(LG)laser pulse in a parabolic preformed plasma channel is analyzed by means of the variational method.The evolution equation of the spot size is derived including the effects of relativistic self-focusing,preformed channel focusing,and ponderomotive self-channeling.The parametric conditions of the LG laser pulse and plasma channel for propagating with constant spot size,periodically focusing and defocusing oscillation,catastrophic focusing,and solitary waves are obtained.Compared with the laser pulse with fundamental Gaussian(FG)mode,it is found that the effect of vacuum diffraction is reduced by half and the effects of relativistic and wakefield focusing are decreased by a quarter due to the hollow transverse intensity profile of the LG laser pulse,while the effect of channel focusing is the same order of magnitude with that of the FG laser pulse.Thus,the matched condition for the intense LG laser pulse with constant spot size is released obviously,while the parameters of the laser and plasma for the existence of solitary waves nearly coincide with those of the FG laser pulse.
基金supported by the National Natural Science Foundation of China(Nos.61665006,61661028,61565012,and 61378062)the Natural Science Foundation of Jiangxi Province(Nos.20161BAB212041,20162BCB23012,and 20171ACB21018)
文摘The fluorescence from the out-of-focus region excited by the sidelobes of a Bessel beam is the major concern for light-sheet fluorescence microscopy （LSFM） with Bessel beam plane illumination. Here, we propose a method of applying the subtractive imaging to overcome the limitation of the conventional LSFM with Bessel beam plane illumination. In the proposed method, the sample is imaged twice by line scanning using the extended solid Bessel beam and the ring-like Bessel beam. By subtracting between the two images with similar out-of-focus blur, the improved image quality with the suppression of the Bessel beam sidelobes and enhanced sectioning ability with improved contrast are demonstrated.
