The stimulated Raman scattering (SRS) is one of the parametric instabilities, which is developed in the underdense region (below quarter-critical density) of laser-produced plasmas. SRS can be simply characterized as a decay of incident pumping electromagnetic wave in another electromagnetic wave and in a fast forward going electrostatic Langmuir wave. Very well known feature of large amplitude electrostatic waves propagating through a plasma is the trapping and the accelerating electrons. Discovery of the wave acceleration has led to an intense study of this phenomenon mainly in the context of laser fusion experiments in the recent years. For investigating the Stimulating Raman Scattering (SRS), we simulate this process for the plasma situation that is available in the spherical tokamaks. For this purpose, we use the XOOPIC code that is a program used to simulate the laser plasma interactions. Then the time evolution of the electron distribution function and the energy transferred to the plasma is obtained. In the next step, we study nonlinear temporal evolution of SRS process in presence of combined effects of relativistic and ponderomotive nonlinearities taking into account the coupling between pump, scattered and plasma waves, in completely ionized plasma. The plasma is considered to be cold and it is assumed that electron thermal velocity is small compared to their quiver velocity under the influence of the laser field For this porpuse, we introduce the basic equations that govern the dynamics of SRS process. Then we use mode coupled equations for three wave process under present approach and then use it to obtain separate set of equations describing nonlinear time dependent evolution of amplitudes and phases of the pump, scattered and plasma waves. In the last step, We study and discuss numerically the nonlinear coupled evolution of SRS process in some special circumstances.
