The Far-Filed Focusing Spot Resolut Enhancing Algorighms Of Laser Amplification Process

High power laser system is an important driving source in the research of inertial confinement fusion (ICF). Because harsh conditions and expensive costs are necessary in high power laser experiments, computer numerical simulation has become an important supplementary method to model the process of amplification and propagation of high power laser. It can not only predict some of the important physical phenomena, but also be an important tool for the optimization design of high power laser system.In the design of numerical simulation software of laser amplification and propagation, when the laser beam are sampled, the calculation scale and the number of the grid should be selected carefully to fulfill the physical requirements both amplification and propagation. So the calculation scale is limited. Take a disk amplifier for an example, the calculation scale only need a little wider than the two-dimensional size of neodymium glass. The consequence of this is that the spatial resolution of the calculated focus results is obviously insufficient, and only a sharp peak value is formed. So the research focus of this thesis is to explore the calculation method of improving the laser far-field focusing spot resolution in the case of limited two-dimensional calculation scale. The main work of this thesis is as follows:1. By expanding the calculation scale of laser beam, the laser far-field focusing spot resolution can be improved. However, the resolution is increased at the expense of the computation of the number of grid. Correspondingly, the consumption time is also increased. Based on the fact that the energy of the laser beam tends to zero when beyond the effective calculation range, the range of calculation can be expanded by zero-padding. Under this premise, through the derivation and compare of the far field focusing transmission before and after zero-padding, it is proved that the transmission results before zero-padding can be used to reconstruct the high resolution data after zero-padding, and the corresponding mathematical expressions are given.2. Based on the theoretical results, the calculation method of improving the laser far-field focusing spot resolution in the case of limited two-dimensional calculation scale and the number of grid is studied. First, we have carried out the optimization of the Fourier transform code in the process of transmission calculation, and a serial algorithm for resolution enhancement is designed and implemented with code on the foundation of the vector marking algorithm. Secondly, using the OpenMP parallel library based shared memory, the parallel algorithm of resolution enhancement is also completed. The dual core and single core calculation results show that the speedup reached 1.72.3. In order to display the spatial distribution of laser beam visually, this thesis studies the translation, rotation, scaling and other geometric transformation algorithms of 3D graphics by using OpenGL drawing function library, and then the 3D display of the calculation results of laser beam transmission is realized.