The effect of a negatively chirped laser pulse on the evolution of bubble structure in nonlinear bubble regime

摘要

In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The Carrier-Envelope Phase (CEP) breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional particle-in-cell simulations show that the utilization of a negatively chirped laser pulse is more effective in controlling the pulse depletion rate, and consequently, the effect of the CEP in the bubble regime. The results indicate that the pulse depletion rate diminishes during the propagation of the pulse in plasma that leads to postponing the effect of Carrier-Envelope Phase (CEP) in plasma response, and therefore, maintaining the stability of the bubble shape for a longer time than the un-chirped laser pulse. As a result, a localized electron bunch with higher maximum energy is produced during the acceleration process. Published by AIP Publishing.