Dear Saumendra,
Thanks for your inquiry;
In a waveguide coupler project, you may define the two waveguides, WG1 and WG2 (see the figure on page 144 of the OptiGrating Manual) each as a multi-layer slab structure. Please make sure the last region of WG1 and the first region of WG2 have exactly the same constant refractive index and the number of steps set to 1 for both; This forms the common layer for joining the two waveguides. The “distance” parameter in the “Waveguide Coupler Profile” tab sets the width of this common layer i.e., the distance between the waveguides. Note: the widths defined for the last region of WG1 and the first region of WG2 are both redundant.
Kind regards,
Amin