Self-Trapping of Extreme Light

We use the qualitative, simplified modeling, and approximately self-consistent nonlinear-optical approaches to explain the nature of the regime under which relativistically intense laser pulses propagate in a plasma to distances exceeding the Rayleigh length considerably, as was found earlier by numerical simulation. Such a regime requires certain matching of the size of the laser spot with the plasma density and the laser pulse intensity. It corresponds to the so-called self-trapping of radiation, which has been well known since the 1960s for the quadratic nonlinearity of the medium's dielectric permittivity and, as has been established, takes place for the relativistic plasma nonlinearity as well. The case of the plasma with a near-critical density is considered as it is of greatest interest in the context of practical applications. Synchronization of chaotic motions of the electrons accelerated by the laser pulse in the self-trapping regime is discussed.