I am trying to design a waveguide coupler with the SiO2 as top cladding medium (n=1.444) and used the modal solution (FDE and EME) to find out the phase matching point for coupling.
The waveguide width (W1) we found to be 345 nm to achieve a good coupling. Then by using EME solver the complete waveguide propagation has been simulated (result screenshots are attached).
The simulated result shows no power coupling from the slot waveguide (W2) to the simple rib waveguide (W1). We have considered much higher waveguide length compared to the coupling length calculated from the FDE mode solution.
The simulation model is attached here. Could you please help me to find out the problem in this model? I will appreciate any help on this matter.