Research On The Propagation Of Ultra-intense Laser Pulses In Micro-tubes And Applications

The rapid development of ultra-intensity laser pulses puts forward higher requirements for laser intensity.In this paper,the particle simulation method is used to conduct related research on how to further increase the laser intensity and strengthen the application of ultra-intensity laser pulses.The main work includes the following three parts: the propagation of Laguerre Gaussian vortex beams in micro-tube;the enhancement of laser pulses by the cone-entrance-tube array;the laser oxygen ion acceleration research;The results of the study are as follows:Firstly,we found that the Laguerre Gaussian vortex beam produced a stronger relativistic nonlinear focusing effect during the propagation process in the micro-tube,which resulted in a stronger laser intensity,and the beam in the tube still maintained the basic properties of vortex light.We also studied the effect of different initial laser intensities on the laser focusing.Further studies have also found that by changing the micro-tube radius,the focus point of the vortex beam in the micro-tube,the focal spot radius of the beam and the amplification of the light intensity can be effectively controlled.Under the condition of optimal micro-tube radius,the light intensity in the tube can be increased by about 4.5 times.Secondly,study the cone-entrance-tube array to enhance the intensity of relativistic laser pulses.The results show that the use of cone micro-tube can effectively reduce the reflected light at the entrance,and further increase the peak light intensity of the laser in the tube.When the laser is off-axis incident,the appropriate off-axis offset will further increase the peak light intensity in the tube.At this time,a stronger nonlinear focusing effect occurs than when the laser is on-axis incident.When the off-axis displacement is too large,the laser cannot enter a single cone micro-tube,so we designed a cone-entrance-tube array so that the laser always has the opportunity to enter one of the tubes,and found that the laser pulse is under the same off-axis conditions,the use of arrays has a better effect on light intensity amplification.Even if the laser is incident on the cone tip of the adjacent structure of the cone-entrance-tube array,two enhanced laser pulses will be generated in the two adjacent tubes,so the cone-entrance-tube array can effectively reduce the influence of the beam pointing fluctuations.Thirdly,studies have shown that in the near-critical density plasma,the electron bubble structure can effectively accelerate oxygen ions,and the energy of the accelerated oxygen ions can reach Gev.At the same time,the evolution of the laser electric field is analyzed,and the acceleration process of oxygen ions in the bubble is described through a one-dimensional analytical model.Further studies have shown that tritium ions as a background plasma have a great influence on the acceleration of oxygen ions,when tritium ions are the main component of the plasma,oxygen ions are accelerated more effectively in the bubble structure.