Relativistic Stimulation Raman Scattering And Atto-second Pulse Generation By Particle-in-cell Simulations

The interaction between relativistic laser pulses (I >10¹⁸W/cm²) and plasmas, a new regime in physics, has been opened due to the development in ultra-short ultra intense laser technology during the past decade. Two questions about relativistic laser pulses interactions are studied in this article: Stimulated Raman Scattering (SRS) driven by a relativistic laser beam; the relativistic nonlinear Thomson scattering (RNTS) of a single electron by interacting with an ultra short ultra intense laser pulse.The first and second chapters are devoted to introduce the conceptions and the developments of Plasma and Laser-Plasma interaction and the particle-in-cell (PIC) simulation.In the third chapter, by using 2D3V PIC simulation code, a relativistic stimulation Raman scattering (SRS) excited by a relativistic laser beam propagating in either medium density plasma or tenuous plasma is studied. For the relativistic SRS in a plasma with density greater than 0.25 n_c (n_c is the plasma critical density), the forward scattering mode and backward scattering mode combines with each other and grows up into saturation in a few laser circles. The electrons are accelerated by the Langmuir wave in SRS. For the relativistic SRS in plasma with density smaller than 0.1 n_c, the side-scattering SRS is the primary mode. The electrons moving in the incident and side-scattering electromagnetic field will be heated via the stochastic-heating-mechanism.The fourth chapter mainly investigates the physical theory and the numerical simulation of the relativistic nonlinear Thomson scattered (RNTS) radiation by a single electron, such an x ray radiation is produced in a specific direction with a very narrow angular divergence, we gain an atto-second (as) pulse with a pulse width of 1 as.