Dynamical behavior and modulation instability of optical solitons in nonlinear directional couplers

In this paper, we focus on the dynamical behavior and modulation instability of optical solitons in nonlinear directional couplers. The expressions of single soliton solutions are derived, and the hyperbolic secant-type pulse is used to excite the input channel. We discuss the dynamical behavior of single optical soliton in traditional directional and negative index material couplers with varying self-phase modulation. Subsequently, based on the linear stability analysis, the distribution of modulation instability gain is studied, and the effect of dispersion, nonlinearity and input power on modulation instability gain is given. It is worth noting that the physical information neural network algorithm performs well in simulating the transmission of an optical pulse in the coupler and leading to some novel optical waves. The results are helpful in understanding the generation of soliton-like excitation and lay a foundation for exploring novel optical soliton in nonlinear directional couplers.