Modulational Instability of a Self-Guided Laser in a Magnetized Plasma Channel

A self-guided laser propagating in a plasma channel in the direction of static magnetic field is unstable to a plasma wave perturbation comoving with the laser with its group velocity. The plasma wave amplitude has a radial profile with a maximum on the axis. As the plasma wave propagates, it causes focusing of the part of the laser that propagates with the electron density trough and defocusing of the part moving with the crest. This creates an axial gradient in the intensity of the laser, exerting a ponderomotive force on the electrons that drive the plasma wave, which leads to the growth of the instability. The growth rate is enhanced as laser frequency approaches the electron cyclotron frequency. The azimuthal magnetic fields have weaker effect on the modulational instability