Learning Forum

[arvind_007]

Can anyone please explain where one should apply the DFT monitor to record the electric field enhancement on a nanoparticle or assembly of nanoparticles?

[Guilin Sun]

Depending on which domain (frequency or time), point/plane/volume average you wish, you can add time monitors where the enhancement is strong, or frequency-domain monitors of a point (I personally do not recommend this as it will depend on the mesh size), line, plane or even volume monitors to find where the strongest enhancement is located, or may do a small region average. and what source you use to excite? if it is a dipole source, I would suggest to avoid the dipole location.
Please refer
Fluorescence enhancement
Surface-enhanced Raman scattering
Purcell factor of a microdisk
Nanohole array
Mie scattering (FDTD)

[arvind_007]

Thank you for your comments.
We're using the TFSF plane wave source for our simulation. The simulation model is simple with nanostructures inside followed by mesh region and then TFSF source. Our query is now the positioning of the Frequency domain field and power monitor for recording field enhancement on the nanostructures. Should it be placed inside the mesh region or outside the TFSF source?
Is it also advised to include the source field inside the meshing region for better results or it is the nanostructure that should be meshed only??

[Guilin Sun]

This will need to understand how does TFSF work: inside TFSF it is the total fields, eg, just like you use a plane wave to get the result. Outside TFSF it is the scattering fields, which means it is the result of the total fields minus the direct illumination: Optical Sources - TFSF Source - Physics & Applications
Understanding source normalization in the TFSF source
If you want the electric field enhancement, the monitor has to be inside the total field.

We recommend to have uniform mesh for the TFSF region in order not to distort the local plane wave nature.

[arvind_007]

Dear gsun,
I have read all the details about the working of the TFSF source. However, in the case of multi-layer stack or gap regions, uniform meshing is a must for the directions normal to the propagation direction of the source. Therefore, if we have to avail the uniform meshing in two directions and non-uniform in the third. That said, is it like applying the multiple meshing in the simulation or it is possible with the help of the mesh override function. If yes, how can we do the different meshing in one simulation region?
Thank you for your time.

[Guilin Sun]

You can have more than one override mesh regions. However, since it has buffer and the change from one override region to another override region, it may not create the mesh you expect. Eg, each layer has integer number of meshes as you define. Please refer this post: Ansys Insight: About override mesh in FDTD Solutions: its use and settings

[arvind_007]

Dear gsun Thank you for your prompt response to my query. Your comments and the link provided helped a lot in clearing my doubts.
Best regards
Arvind