Ponderomotive interactions between a laser pulse and preformed micro-scale plasma

The study of ponderomotive interactions between a laser pulse and plasma are important for many applications. These include stimulated Raman/Brillouin scattering processes and Terahertz (THz)/microwave emission from femtosecond filaments. Our goal is to study the ponderomotive interaction between a propagating laser pulse and a preformed micro-plasma. As the laser propagates across the micro-plasma, ponderomotive forces perturb the electron distribution and generate a current. To model this process, a beam propagation model describing the pulse propagation dynamics is coupled to a kinetic model that describes the response of the plasma via the laser-induced ponderomotive force. The forces acting on the electrons consist of the electrostatic force, ponderomotive and radiation pressure forces. The electron distribution function is determined by solving the nonstationary one-dimensional Boltzmann equation in the Bhatnagar-Gross-Krook (BGK) approximation. The electrostatic field is determined using the Poisson equation. Self-focusing (Kerr effect) and plasma defocusing are accounted for in order to capture the impact of these processes on the forces driving the electron dynamics. Preliminary results will be presented that show how the current resulting from the ponderomotive interaction is impacted by relevant parameters (laser intensity, plasma density, etc.). Implications of these results for emission at THz and microwave wavelengths will be discussed.