Second-harmonic generation of hollow Gaussian laser beams in inhomogeneous plasmas in the presence of wiggler magnetic field

Abstract

Second-harmonic generation of hollow Gaussian laser beams (HGLBs) in inhomogeneous plasmas is investigated in the presence of an external wiggler magnetic field. The wiggler magnetic field and electric field of the laser pulse exert a ponderomotive force on electrons deriving electron velocity. Electron velocity, wiggler magnetic field and magnetic field of the laser pulse beat to exert a nonlinear ponderomotive force on electrons at the second-harmonic frequency. The nonlinear ponderomotive force can derive a nonlinear current density. Using linear and nonlinear current densities and wave equation in cylindrical coordinates, two equations obtaining different components of the electric field of second-harmonic wave (SHW) are derived. Results indicate that by increasing the external wiggler magnetic field, order of HGLB, rippled electron density, rippled wave number and initial intensity of the laser pulse, the amplitude of the excited SHW increases. Finally, it is found that by decreasing the initial width of the laser beam, the amplitude of SHW increases, attains a maximum and then decreases.