Spatial weak-light solitons in an electro-magnetically induced nonlinear   waveguide
  We show that a weak probe light beam can form spatial solitons in an electro-magnetically induced transparency (EIT) medium composed of four-level atoms and a coupling light field. We find that the coupling light beam can induce a highly controllable nonlinear waveguide and exert very strong effects on the dynamical behavior of the solitons. Hence, in the EIT medium, it is not only possible to produce spatial solitons at very low light intensities but also simultaneously control these solitons by using the coupling-light-induced nonlinear waveguide. 
Tao Hong