Convergence issue

fdtd

#1

I am trying to get the plasmonic modes on a gold nanowire placed over a gold thin film.
Please find the example1.fsp file attached.
I am not able to get the results converged.
Your help will be greatly appreciated.
Also attached, the log file corresponding to example1.fsp.

Please find the the auto shut off level is not decreasing.

example1.fsp (278.0 KB)
example1_p0.log (9.6 KB)

Thank you,
Ameen.


#2

Hello,
When box monitor is placed to find the scattered fields and absorption fields along with a TFSF source,the T value is sometimes greater than 1. If this is the case, the way to solve this problem is to re-normalize the transmission to the sourceintensity instead. Like this analysis group in the Mie scattering example.
Apparently, this issue has been described already. Here are the relevant links:
https://kb.lumerical.com/en/index.html?ref_sim_obj_tfsf_power_normalization.html
This page provides a thorough method for convergence testing of results from an FDTD simulation, so you can determine the possible sources of error in a simulation, and quantify the level of convergence.
https://kb.lumerical.com/en/index.html?layout_analysis_test_convergence_fdtd.html.
Hope this helps!


#3

The answer by 1130344 is not clear at all.
It seems to me that, you have not looked into the attached simulation file.

First of all, I am not using any TFSF source.
Moreover, I am not interested in calculating scattering.

I am looking for the field around the nanowire at different incident frequencies.
But the auto shut off level is not decreasing.
This means that the field is not dying out inside the simulation region.
I am seeking help on this.

Thank you!!


#4

Hi @mohamedameen.p

The simulation file is too large and I am interested to know more about the experimental setup so that we can reduce the simulation time.

For starting point, can we run 2D simulations assuming that rod has infinite size? We can also use dipole source and time monitor to look at the field spectrum. The source bandwidth is also large and it is also probably affecting simulation time. All of this is important to make sure that auto shutoff level decrease as expected.

Then we can start a 3D simulations using a dipole source. How the length of the nanowire can affect the simulation results?


#5

Thank you for the response.
I will try your suggestions.
Will update here.

Ameen.