ABSTRACT
The stability of an input light beam under various physical situations is one of the most exciting issues of modern nonlinear optics. One such stability criterion leads to the phenomenon of modulational instability (MI). The history of MI dates back to mid 1960s, courtesy of Lighthill, who is responsible for the famous Lighthill criterion, which sets the conditions for the stability of the plane wave in a nonlinear medium. Considering the importance of higher order dispersion, the impact of fourth order dispersion in the MI dynamics of a relaxing saturable nonlinear system is investigated. The chapter discusses the influence of nonlinear relaxation in the MI dynamics of vector MI with higher order dispersion. It explains the interplay between nonlinear relaxation and coupling coefficient dispersion in a nonlinear directional coupler. The chapter explores the influence of nonlinear saturation in the MI of a two core fiber with the effect of coupling coefficient dispersion.
