A simple but accurate formalism for study of single -mode graded index fiber directional coupler in presence of Kerr nonlinearity

This paper presents performance of directional coupler consisting of two identical single-mode graded index fibers in presence as well as in absence of Kerr type nonlinearity. In this context, parabolic and step index fibers of some typical V numbers are used. Here, we employ a simple series expression for fundamental modal field for such fibers prescribed by Chebyshev formalism. Analytical expression of the coupling length of the directional coupler is formulated. Here, we apply method of iteration in order to take care of nonlinearity. The concerned evaluation involves little computation. Thus, the formalism developed for study of nonlinear directional coupler can be treated as an accurate but simple alternative to the existing complicated methods available in literature. This user friendly method will prove beneficial to the scientists and technologists working in the field of nonlinear optics. © 2020 Elsevier GmbH