Relativistic laser plasma interactions: Pulse shape modification and magnetic field generation

We report on two important features of the interaction of a high intensity ultrashort laser pulse with a plasma: a) the use of induced relativistic transparency for preparing pulses with an appropriate shape (sharp leading and/or rear edges) by making them propagate through a thin high density plasma foil, b) the formation of a quasi-steady magnetic field wake, of intensity approaching a Gigagauss, well behind a short relativistically intense pulse in an underdense plasma.