3D FDTD results not converged
I am working on the model verification, but the 3D FDTD results will not converge at the end of the simulation. I have tried finer meshing and longer simulation time, but none of them worked out. Besides, it seems that the autoshutoff level starts to increase at a certain point of the simulation time after I increase the simulation time. Does anyone have any suggestions? Thank you so much!
Currently the model only includes a semi-ring with the radius of 20um and two ports at the both end-faces of the semi-ring.