Coherent manipulation of optical spatio-temporal solitons in four-level sodium atomic medium

The formation and propagation of three-dimensional optical spatio-temporal solitons in a four-level sodium atomic medium are investigated under the influence of the cross-Kerr nonlinearity. The atomic response is analyzed using the density-matrix formalism, from which the linear and nonlinear susceptibilities, group index and group velocity of the medium are derived. By employing a variational approximation, the spatio-temporal soliton envelope is studied in terms of spatial and temporal coordinates during propagation. Significant control over optical spatio-temporal soliton dynamics is reported through the coherent manipulation of applied driving fields and system parameters. Significant control over optical spatio-temporal solitons is reported under the influence of applied fields and system parameters for advanced technology. Single, double, triple, quintuple and septuple spatio-temporal solitons are obtained by adjusting the controlled field Rabi frequencies, detunings and decay rate from excited states. Depending on the nonlinear response of the medium, the solitons exhibit spreading behavior and strong localization int spatial x/λ and temporal τ/τ0 dimensions. Various soliton profile, including bullet, spheroid, superball and ellipsoid like shapes are obtained and shown to propagate stably along the z/λ direction. The modified results indicate the feasibility of coherently controlling complex spatio-temporal soliton structure, which may be useful for potential applications on advanced communication systems and soliton radar technology.