Electron acceleration by a cosh-Gaussian laser beam driven electron plasma wave: extended paraxial theory

摘要

Excitation of electron plasma wave by an intense short laser pulse is relevant to electron acceleration process in laser plasma interactions. This work presents the self-focusing of an intense cosh-Gaussian laser beam in collissionless plasma with relativistic and pondero-motive nonlinearities in the extended-paraxial region. Further, the effect of self-focusing of the cosh-Gaussian laser beam on the excitation of electron plasma wave and on subsequent electron acceleration has been investigated. Analytical expressions for the beam width parameter/intensity of cosh-Gaussian laser beam and the electron plasma wave have been established and solved numerically. The energy of the accelerated electrons has also been obtained. The strong self-focusing of the cosh-Gaussian laser beam in plasmas stimulates a large amplitude electron plasma wave, which further accelerates the electrons. The well-established laser and plasma parameters have been used in numerical computation. The results have been compared with the paraxial ray approximation, the Gaussian profile of the laser beam, and only relativistic nonlinearity. The numerical results show that the focusing of the cosh-Gaussian laser beam, the amplitude of the electron plasma wave, and the energy gain by the electrons increases in the extended-paraxial region, when relativistic and ponderomotive nonlinearities are operative simultaneously. In addition, it has also been observed that the electron plasma wave is driven more efficiently by a cosh-Gaussian laser beam that accelerates plasma electrons to higher energies.