Magnetic field generation with helical laser beams in electron-hole plasmas

A circularly polarized Laguerre-Gaussian (LG) laser beam moves in an electron-hole plasma, producing a quasi-static magnetic field in azimuthal direction. To achieve this, electron and hole momentum equations are solved taking nonrelativistic ponderomotive and Lorentz forces on equal footing. However, the present model neglects quantum effects for low-carrier densities and high
temperatures, also omitting electron-hole thermal pressures compared with ponderomotive force. Electron and hole velocities move along the z-axis to generate the current density according to the Ampère's law, resulting in the azimuthal magnetic field. The latter strongly depends on laser intensity and confirms its behavior in typical semiconducting materials. A high degree of agreement between the analytical and numerical results is found, supporting the validity of the analytical method. Numerically, it is shown that azimuthal and radial mode numbers, pulse amplitude, and hole-to-electron effective mass ratios significantly modify the magnetic field profiles. The present findings only validate a non-relativistic classical electron-hole plasma for which the carrier density must be smaller than the critical density n_e0 ≤ n_cr-.