Mori DMS- 9722121 This is a highly multi-disciplinary proposal for research in modeling high intensity laser-matter interactions. The experiments being modeled are rich and varied in phenomena, such as relativistic self-focusing/self-phase modulation, Raman scattering, and photon acceleration. In this work we will develop a three-dimensional particle-in-cell code to accurately simulate these interactions. The accurate modeling of these experiments will lead to new understanding of laser-matter interactions. The research requires expertise in high-intensity laser-plasma physics, laser plasma accelerations, large scale particle-in-cell computer modeling, and manipulation of large data sets. Recently short-pulse laser technology has advanced to where there has been a great profusion of experimental results and the theoretical understanding of what is happening has not kept pace. In this research, we will develop the capability to accurately simulate what happens when a high intensity short laser pulse interacts with matter. The capability to model these interactions will help experimentalists interpret their results and increase our understanding of the physical processes involved.