Nonparaxial theory of cross-focusing of two laser beams and its effects on plasma wave excitation and particle acceleration: Relativistic case

Cross-focusing of two propagating ultrahigh power laser beams in homogeneous plasma (laser intensity I-L > 0(16) W/cm(2)) has been studied in the nonparaxial region. By expanding the eikonal and other relevant quantities up to the fourth power of r (radial distance), we observed that the focusing of the laser beams becomes fast in the nonparaxial region. The difference in focusing/ defocusing of the axial and off-axial rays leads to the formation of a splitted profile of laser beams in the plasma. A remarkable change is also observed in the amplitude of plasma wave excitation and particle acceleration in the nonparaxial region in comparison to the paraxial region. (c) 2008 American Institute of Physics.