I am trying to simulate a rather complicated plasmonic device and as I am rather new to Lumerical, I feel it is better to work from the Nanohole array example given in the tutorials on this website https://kb.lumerical.com/en/index.html?nonlinear_methodology.html.
I have modified the example including moving the source so that it is shining from above, and changing several geometries.
The biggest modification is that I have inserted a new ‘dielectric’ layer between the ‘film’ and ‘substrate’ layers.
If ‘dielectric’ is thin, I believe I get a reasonable result, however, if ‘dielectric’ is thick I see several features in the transmission that I did not expect.
I assume that this is due to some kind of Fabry-Perot effect when the thickness of ‘dielectric’ is comparable to the wavelength of the light, however, my intuition (from previous experiments, not simulations) is that the result is non-physical. Especially the large number of features when the thickness of the layer is significantly larger than the wavelength.
So, my question is whether my result is indeed correct or whether these features in the transmission are instead just an artefact of either my simulation parameters or the FDTD method in general? If it is an artefact, how can I change my simulation to get a more physical result?
For example, I found described here https://kx.lumerical.com/t/eliminate-interference-effects-in-solar-cell/1211/12 a suggestion to split the device into sections and use a custom source from the monitor data https://kb.lumerical.com/en/ref_sim_obj_create_source_from_simulation.html.
Attached is my Lumerical file and spectra for four thicknesses (50nm,100nm,500nm,3000nm).
Any suggestions will be gratefully received.