Reply To: FDTD:: simulation of directional coupler

[Zhongdi Peng]

Apart from that, my platform has highest index component of 2.21 @ 1.55 um, the effective index of the mode is about 1.8. According to your calculation, the mesh size should be 1.55/1.8  / 6 = 0.1435um (6 splitting points per wavelength) or 1.55/1.8 / 10 = 0.086um. Actually, I also tried with dx, dy, dz = (0.1, 0.1, 0.02) um before and it still diverged with PML layer=16 after auto-shutoff reaching 0.0025. What else do you think I need to optimize for convergence?