Efficient generation of tunable magnetic and optical vortices using plasmas

Abstract

Plasma is an attractive medium for generating strong microscopic magnetic structures and tunable electromagnetic radiation with predictable topologies due to its extraordinary ability to sustain and manipulate high currents and strong fields. Here, using theory and simulations, we show efficient generation of multimegagauss magnetic and tunable optical vortices when a sharp relativistic ionization front (IF) passes through a relatively long wavelength Laguerre-Gaussian (LG) laser pulse with orbital angular momentum (OAM). The optical vortex is frequency upshifted within a wide spectral range simply by changing the plasma density and is compressed in duration. The topological charges of both vortices can be manipulated by controlling the OAM mode of the incident LG laser and/or by controlling the topology and density of the IF. For relatively high (low) plasma densities, most of the energy of the incident LG laser pulse is converted into the magnetic (optical) vortex, with conversion efficiency approaching ∼90% for an ideal IF.