Simulation Of The Bunching Effect Of Accelerating Plasma Blocks And The Generation Of Plasma Gratings In The Interaction Between Ultra Short Intense Lasers And Solid Targets

In the mid-1980s,the chirped pulse amplification(CPA)technology made the laser inten-sity increased by leaps and bounds.The emergence of ultra strong and ultra short pulse laser has broadened the researches on the interactions between the lasers and the matter,giving birth to the discipline of strong field physics.When matter interacts with high-intensity laser,it is very easy to be ionized and produce plasmas,which will lead to a wealth of physical phenomena in the interaction between laser and plasma such as laser acceleration and laser-induced plasma grating generation.The former can not only find applications in basic researches,such as particle and nuclear physics,but also in wide practical applications,such as medical physics and nuclear fusion studies.As to the plasma gratings,it can be used in the control and modulating of intense laser fields and in enhancing of many physical effects,for example,the high-harmonic generation based upon laser/atom interactions in air.Based on the interaction between ultrashort intense laser and solid density plasma target,the particle-in-cell(PIC)simulation method is used to study the bunching of laser accelerated plasma block and a new scheme to generate plasma gratings.The main conclusions are summarized as follows.1.A scheme to bunch a block of accelerated plasma based upon the interaction between gradient density target and an ultra-instense circularly polarized laser pulse with intensity I≈1020 W/cm2 is investigated.The target density decreases linearly along the laser propagation direction.Through intensive parameter optimization,we have observed the bunching of series of plasma blocks behind the target.The ion beam density after bunching increases about one order of magnitude compared with the case using constant-density target.The underlying mechanism can be attributed to the sensitive dependence of the plasma block acceleration upon the target density.2.A new mechanism to generate plasma grating is found based upon the interactions between picosecond intense laser pulses(I～1015W/cm2)and overcritical soliddensity plasma(particle number density n～10nc).It is shown that this plasma grating results from the interference between the plasma waves excited by the strong laser fields in solids.So only one laser beam is needed to generate the gratings.The spatial period of nanometer dimension is greatly different from that of micrometer dimension produced by traditional methods using two counter-propagating lasers in gas-density plasma.Its short space period has high application value for X-ray light control.