We picked this example because we would like to validate our circuit tool by comparing it with direct device simulation of the whole structure. This is the largest structure a device simulation tool can handle on a regular PC even at very coarse mesh.
There are two approaches:
1. Direct device simulation of the whole structure
2. Circuit simulation with custom PDKs by decomposing the whole structure into three sub-devices: polarization rotator, coupler, and splitter.
For the device simulation, the tool we use RSoft RCWA-based ModePROP, which is relatively efficient but maintains accuracy.