Influence of septic nonlinearity on modulation instability under normal and anomalous dispersion regime

In this paper, we presented a detailed investigation on modulational instability (MI) of the higher order nonlinear Schrodinger equation with non-Kerr nonlinearities up to septimal nonlinearities to describe the propagation of attosecond pulses in a dispersive medium. In this study we demonstrate the impact of septic nonlinearity and sixth order dispersion on MI under normal and anomalous dispersion regimes. Investigation shows that MI gain and bandwidth is sensitive to septic nonlinearity and sixth order dispersion in both dispersion regimes. It is observed that at quantitative level the combined effect of fourth order dispersion parameter and sixth order dispersion plays significant role in the generation of nonconventional side bands. Furthermore, the gain control by the septic nonlinearity is clearly observed under different cases of higher order dispersion parameters.