Plasmonic modes of 1D dielectric grating

SPR on grating.lms (281 KB)
For the given symmetry a (line grating with periodicity in the x direction), there is a SPP excitation at 1.4737 um. I would like know the mode characterizations, ie whether the associated mode a symmetric or asymmetric one. It can be understand from the perpendicular or parallel component of the electric field distribution. Kindly help me to fix the FDE solver type as well as boundary condition

Dear @Shereena.Joseph.phys

Thank you for your inquiry.

Symmetric and asymmetric modes can be found from the behavior of electromagnetic field:

For 1D structures, it can be still defined from electromagnetic fields as you can see in the link below:

Please note that this is a symmetric structure (metal - insulator - metal). However, since your structure is not symmetric (air - grating - Ag - substrate), modes are not expected to be symmetric or asymmetric.

Anyhow, I modified your simulation file and used a finer mesh to resolve the Ag layer:

SPR on grating_modified.lms (263.0 KB)

I hope this answered your question, and please let me know of your thoughts.

Thank you bkhanaliloo,

I am able to plot the filed distribution of the mode. However Ex the field distribution of this particular mode is not changing with Ag layer thickness, ie at 19 nm Ag thickness the superposition of two bound mode at both interface of metal are expected to vanish and there expect a corresponding change in the field distribution. Further the effective index value shows a drastic change as I change the FDE geometry only to cover the metal thickness.HzEy

Dear @Shereena.Joseph.phys

Thanks for the update, and sorry for a late reply. We had a long weekend here.

Can you please attach your simulation file for a review? I think the mesh is coarse, but I need to check the simulation files first before making any advice.


I am attaching the file here. I change the FDE geometry to compute the Plasmonic mode in the 40 nm Ag layer, the mode filed distribution exhibiting the bounded mode in Ag layer but the real part of effective index is very high.SPR on grating_modified.lms (288.4 KB)

Dear @Shereena.Joseph.phys

Thanks for the simulation file.

Before moving forward discussing simulation results, can you please explain what is the geometry that you are trying to find the modes for? Do you have any references for your simulations?

My knowledge on plasmonic modes is short, but generally we have an MIM structure in which an insulator is between the metal layers. However, in your case metal is bounded by two insulators. As a result modes are primarily located in the insulators rather than metal.

Once we corrected the geometry, we can run the simulations to calculate the modes.

Please let me know of your thoughts.

Hi, Thank you for your kind support.

The geometry can be found in the attached reference.Mohammad Abutoama.pdf (3.7 MB)
. I am trying to find the Plasmonic mode distribution in both cases given in the reference.


Dear @Shereena.Joseph.phys

Thank you very much for sharing the paper and simulation file with me.

I thought that maybe we can have a step back and first try to replicate the results of the paper.

I used a 2D FDE, and after couple of modifications, I think I found the mode of interest as is shown in Fig 2:

I was not quite sure why you are using 1D FDE? Since grating has a finite size, you should use 2D FDE.

Please let me know of your thoughts and how you want to use this result to find symmetry in your structure. I am attaching my simulation file for your review:

SPR on grating_BK.lms (264.2 KB)


Thank you so much

I need to plot the modal profile along x=0 as given

.Please direct me to plot the mode for a particular direction and axis.

Hi @Shereena.Joseph.phys

To get a linear plot along, say, x=0 axis from the visualizer, run the simulations and then select the mode of interest from Objects Tree as is shown below:


Then right click on the mode, and visualize E, H, P, or farfield. In the visualizer, select a line plot and set x-axis Action to slice:


I hope this suffices your requirements.

You could use scripting language to output the EM fields, which we can discuss it further if you were interested.


Dear bkhanaliloo,

Thank you so much for your support. You may close the case now

Great. I am glad to hear that problem is resolved.