Effects of Radiation Reaction on electron dynamics in Radially Polarized Ultra-Intense Laser Focus Seeded By Field Ionization of High Charge States of Neon

The proliferation of multi-petawatt laser experimental systems all around the world is ushering an exciting era of ultra-intense relativistic laser plasma interaction (RLPI) physics. RLPI experiments with complex polarization states are becoming feasible and have motivated interests in radiation reaction (RR) effects. Electron dynamics in a strongly relativistic electromagnetic field are significantly altered by radiation friction force. In this work, we perform a computational investigation of direct acceleration of electrons produced during ionization of underdense neon gas using a tightly focused and radially polarized Petawatt-class short pulse laser by numerically solving the relativistically invariant Lorentz equation incorporating the Landau-Lifshitz form of radiation damping effects. For comparison, we also solve the Lorentz equation without RR force. Semi-classical tunneling ionization and Monte Carlo type sampling of the focal volume are considered in both cases. We observe that the RR force linked with the dissipation of kinetic energy of electrons, which we observed in linear polarization, can also contribute to a significant gain of energy in the case of radial polarization. This phenomenon is directly linked to the radial polarization state of the incident laser beam that results in a strong longitudinal electric field (Ez) when tightly focused, where electrons ionized near the focal center in the presence of RR force experience an important gain of kinetic energy of at least 10% compared to those ionized in absence of RR force.