Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation

The efficiency of laser overdense plasma coupling via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed over a wide range of laser pulse intensity from 10¹⁵ to 10²⁰ W cm^-2 μm² with electron density ranging from 25 to 100n_c to describe the laser interaction with a grating target where a surface plasma wave excitation condition is fulfilled. The numerical studies confirm an efficient coupling with an enhancement of the laser absorption up to 75%. The simulations also show the presence of a localized, quasi-static magnetic field at the plasma surface. Two interaction regimes are identified for low (Iλ²< 10¹⁷ W cm^-2 μm²) and high (Iλ² >10 ¹⁷ W cm^-2 μm²) laser pulse intensities. At "relativistic" laser intensity, steady magnetic fields as high as ∼580 MG μm/λ₀ at 7× 10¹⁹ W cm ^-2 μm² are obtained in the simulations.