Using the Steepened Plasma Profile and Wave Breaking Threshold in Laser-Plasma Interaction

In this work we evaluate the interaction of high intense laser beam with a steepened density profile. During laser interaction with underdense plasma by freely expanding plasma regime, modification of density profile is possible. In this paper we have investigated the ultra short laser pulse interaction with nonisothermal and collisionless plasma. We consider self-focusing as an effective nonlinear phenomenon that tends to increase when the laser power is more than critical rate. By leading the expanded plasma to a preferred location near to critical density, laser reflection is obtained, so the density profile will be locally steepened. The electromagnetic fields are evaluated in this new profile. We show the amplitude and period of electrical field oscillation are increased by reducing the steepened scale length. Also our numerical results identify that by reducing the steepened scale length, the electrical field is increased to wave breaking threshold limit. This high gradient electrical fields causes the effective beam loading during the wave breaking phonomenon. The wave breaking can be the initial point for other acceleration regime as cavity or channel guiding regime. (C) 2008 WILEY VCH Verlag GmbH & Co, KGaA. Weinheim