Relativistic and Charge-Displacement Self-Channeling of Intense Ultrashort Laser Pulses in Plasmas

Abstract

Relativistic and charge-displacement self-channeling is one of the most significant phenomena in the entire area of the interactions of extremely intense laser pulses with matter. Both the relativistic increase in the mass of laserdriven plasma electrons and the reduction of electron concentration under the effect of the ponderomotive force tend to reduce the local electron frequency in a laser-irradiated plasma. As a result, the simultaneous modification of the plasma dielectric response by the propagating electromagnetic radiation via the above two mechanisms enhances the medium transparency in the paraxial domain where the intensity is maximal. Under certain conditions discussed in this chapter, this effect leads to the emergence of channeled regimes of superintense laser pulse propagation in underdense plasmas. In these regimes, the laser radiation diffraction is suppressed, nonlinear beam self-trapping occurs, and the laser pulse propagates into the plasma over dozens of Rayleigh ranges. An additional electromagnetic radiation confinement mechanism emerges due to electron cavitation, namely, the total expulsion of the electron fluid from a certain spatial area. Then, the laser beam propagates within the resulting channel, where the intensities can reach the level of 10²² W/cm².