Coupled-mode description of fibre-to-two-layered planar waveguide coupler

Abstract

A coupled-mode model is presented, which describes the behaviour of a complex waveguiding system consisting of a single-mode optical fibre evanescent field coupled to a planar waveguide which consists of two layers (overlay waveguide and superstrate layer). The real two dimensions of the waveguide cross-sections are taken into account, as well as the transverse electric or transverse polarization of the planar waveguide modes. This model provides a proper quantitative description of the coupler, revealing the influence of the superstrate layer onto the light transfer into the coupler. Some possible applications of such an in-line fibre device are considered.