Grating assisted couplers have found wide usage in many areas of photonics such as filters, optical switches, WDM systems, and as feedback mirrors for several laser types. This example is based on those found in discussions by N. Izhaky et. al. [1].
The coupler used in this example consists of three sections: two waveguides separated by an index-modulated grating. This structure appears in the CAD as:
For this simulation, the modes of both waveguides were computed and used for the analysis. The computed spectral response for this structure is:
This result shows both the forward and backward reflection spectrum for the modes in both waveguides.
[1] N. Izhaky and A. Hardy, Analysis of grating-assisted backward coupling employing the unified coupled-mode formalism, J. Opt. Soc. Am., 16, 1303 (1999).