Magnetically induced transparency of circularly polarized laser beam in plasmas

The interaction of intense short laser pulse with plasma involves a number of interesting nonlinear physical phenomenons, including the generation of quasi-static intense magnetic fields. The recent achievement of powerful short laser pulse has lead to renewal interest in interaction of radiation with matter into relativistic regime. The generation of magnetic field in high intensity laser-plasma interaction has received considerable attention these include fast electron and ion generation, indicating that ultra strong electric field and magnetic field are generated in the plasma.

The development of multi terawatt femtosecond lasers makes it possible to achieve a regime of laser matter interaction never reached before. New interaction mechanisms are being proposed theoretically to model the interaction, including the anomalous skin effect, hole boring and self induced transparency. During the interaction of an intense laser with plasma, a magnetic field is generated and betatron resonance occurs between the electron and the electric field of the laser, and the electrons are accelerated to high energies. In this new regime of high laser intensity the quiver velocity of electrons is relativistic; one of the main effects in laser plasma interaction is associated with the relativistic increase of the inertial electron mass and consequent lowering of the natural plasma frequency that may crucially modify the optical properties of plasma. The superintense electromagnetic radiation would be able to propagate through a classically overdense plasma due to the relativistic correction to the electron mass, the so-called induced transparency effect.

In the present paper we describe propagation of circularly polarized high-intensity laser radiation in plasmas. The propagation of an electromagnetic wave in magnetized plasma, in the so-called extraordinary mode has been considered. Such a wave field causes the plasma electrons to gyrate in the orbit whose radii depend on the radiation intensity, on the wave frequency and on the electron density. This gyration of the plasma electrons induces a magnetic field, which for the left circular polarization is parallel and for right circular polarization is antiparallel to the direction of wave propagation.