Learning Forum

[Jeon]

Hi
I am checking the transmittance of several combinations of nanopost arrays.

Some simulations diverged (probably?) due to strongly resonating structures. So I fixed the diverging simulation by changing the PML profile setting to stabilized. However, now the transmittance value is greater than 1.
So I compared the same simulation configuration except for the PML profile setting (using a simulation configuration where the PML profile setting does not diverge even in the standard) as shown below.

Also, in the stabilized setting, using the movie monitor, I found the following strange phenomenon. That is, it was found that energy was released from the PML area after a considerable time elapsed after the application of the pulse.

Why is this happening and how can I fix it?

Thank you so much.

[Guilin Sun]

First, please make sure that the structure periodicity is correct. Is this a 45-rotated rectangular lattice or hesagonal lattice?

If it is rotated rectangular periodicity, you may not need to rotate it, except there is a necessary.

DIverging can be due to several different issues, such as large diffraction angle (then use Steep Angle PML with 64 layers), PML too close to structure (increase z span); It is not necessarily to use the Stabilized PML, which may stablize the simulation but result  can be incorrect. Please refer this

Troubleshooting diverging simulations in FDTD – Ansys Optics

Large than 1 usually means the simulation does not run long enough, the autoshutoff min is not reached etc. Most likely this current configuration has very large diffraction angle. Please use visualizer to check the farfield with assuming periods 10 by 10. or use grating analysis: 

Diffraction grating – Ansys Optics

[Jeon]

Your answer was helpful.

It would be nice if you properly moved the precious post below.

Ansys Insight: Transmission results greater than one

Thank you very much.