Tunneling of a relativistic laser pulse through an overdense plasma slab

An ultra-fast super-radiant laser, with Gaussian radial intensity profile, when impinges on an overdense plasma slab, induces large oscillatory velocity on electrons raising their mass and lowering the plasma frequency. The ponderomotive force driven electron cavitation further lowers the plasma frequency. These effects are pronounced for the central portion of the beam and weaken as one moves away from the laser axis. Consequently, central portion of the beam tunnels through the plasma slab, while the marginal rays are blocked. The output beam thus has a smaller spot size. It also possesses a curvature in the wavefront that may help diagnostics.