Grating-assisted coupling of highly asymmetric dielectric waveguides

This paper discusses an accurate method for the calculation of the coupling problem for highly asymmetric waveguides. The method is based on Floquet-Block modes and provides a rigorous electromagnetic solution of the grating-assisted directional couplers (GADC). The grating period (Λ) and coupling length (Lc) can be accurately predicted even though the structure may have a strong grating, and the waveguides are highly dissimilar. This approach results in two dominant solutions; one solution has a 'symmetric' field distribution about the center of the two guides, whereas the other is 'asymmetric'. This new method allows the design of semiconductor lasers monolithically coupled to fiber-like waveguides to produce WDM sources that can be easily coupled to optical fibers.