Excitation of ring solitons and dromions in a non-isospectral nonlinear Schrodinger equation with tunable external potential

In this work, the existence of nonlinear ring waves in the form of multi-solitons is investigated analytically by considering a non-isospectral Nonlinear Schrodinger (NLS) equation with external potential. In order to generate soliton solutions, Darboux transformation technique is employed based on the Lax pair. Due to inhomogeneous effect of non-isospectral parameter, we attained the various form of ring solitons. Moreover, transformation from bright ring to dark ring and dromion structure are also observed for the first time. This indicates that the structure of nonlinear wave is strongly dependent on the combined effects of non-isospectral functions and external potential. To illustrate the physical significant of the considered equation and obtained solutions, the 2D and 3D graphs are successfully plotted by selecting appropriate values of control parameters. Finally, we perform linear stability analysis on non-isospectral Nonlinear Schrodinger (NLS) equation to demonstrate the gain spectrum for different strength of nonlinearity.