  We consider theoretically the dynamics of electric currents optically
injected in carbon nanotubes. Although the plasma oscillations are not seen in
these systems, the main effect on the carrier's motion is due to strongly
nonuniform space-charge Coulomb forces produced by time-dependent separation of
injected electron and hole densities. We calculate evolution of the dipole
moment characterizing the time- and coordinate-dependent charge density
distributions and analyze different regimes of the dynamics. The developed
time-dependent dipole moment leads to a dipole radiation in the THz frequency
range for typical parameters of injected currents.
