Learning Forum

[emh711]

The light source that I am using is a Gaussian source. The structure that I am simulating is a nanohole.

My simulations typically end at an auto-shutoff level of 0.0002 or 0.0004.

Is this too high?

Can this cause inaccurate results?

[Kyle]

The autoshutoff level is a measure of the energy left in the simulation region. If the simulation ends before the fields have sufficiently decayed, this can lead to inaccurate frequency domain results, as discussed in this post:
/forum/discussion/25276/simulation-time-and-frequency-domain-monitors/p1
The default autoshutoff threshold level of 10^-5 is low enough for most simulations, so 2*10^-4 is probably too high. I would recommend that you increase the simulation time until the autoshutoff level reaches the default threshold level of 10^-5.

[emh711]

I see. I placed a time hole and time corner close to the bottom of the simulation region.
The power from both time hole and time corner appear to decay close to 0.
Time Hole (Power)
Time Corner (Power)
Does this mean that the simulation results are okay to be seen as accurate?
And, what are some of the steps that can be taken to increase simulation time?

[Kyle]

Does this mean that the simulation results are okay to be seen as accurate?
Not necessarily, this is only a measure of the fields at one location, so even if the fields appear to have decayed to zero here there might still be fields circulating in other parts of the simulation region. The autoshutoff level should be used to determine if enough of the light has left the simulation region to end the simulation.
And, what are some of the steps that can be taken to increase simulation time?
The simulation time is a setting of the FDTD solver object:
The simulation will end either at the simulation time or when the autoshutoff min level is reached. In most cases it is best to end the simulation when the autoshutoff min is reached, so if your simulation is ending due to the simulation time, the simulation time should be increased.