Effective index method with built-in perturbation correction for the design of polarization-insensitive optical waveguide directional couplers

Abstract

In this paper, we apply the recently proposed effective- index method with built-in perturbation correction to the study of direcitonal coupler that consists of two parallel rectangular-core waveguides. We show with numerical examples that the splitting ratio of the directional coupler can be made insensitive to the polarization state of the input light by using proper waveguide parameters.