Here we study the problem of a focused laser beam
propagation in plasma with the initial density, which is
much higher than the critical one. The Helmholtz equations,
together with the equations of single fluid hydrodynamics,
with the relativistic ponderomotive force were solved.
It was shown that the stable waveguide with the cross-section
of wavelength size was formed when plasma was affected
by the laser radiation with the intensity exceeding the
critical one while the laser radiation pulse was as long
as (10–100) ps.