Extinction cross-section from a hexagonally arranged array of metallic nanoparticles using TFSF source

fdtd
scattering
tfsf
periodic

#1

Hello,
I would like to calculate extinction cross-section from ‘infinite’ periodic array of metallic nanoparticles that are hexagonally arranged, while using a TFSF source that I have been using for single nanoparticle case.
I tried enclosing one particle in the array and using PBC or Bloch boundary conditions to obtain the extinction cross-section, but the result I get seems identical to the single nanoparticle case I have been doing, so I am not sure if I am doing it correctly. So I tried setting up the mesh in the way shown in the image, and of course I get a strange result. Could you please teach me how to set up the simulation correctly for this? I’ve included the .fsp file.

Thank you.

Sean Park


Hex_arranged_array_example.fsp (511.1 KB)


#2

Hi,

Typically one use the Bloch boundary condition if the angle incidence is not zero. For your system, you have to use either a periodic boundary condition for x & y. Alternatively, you can further minimise the calculation size with symmetry.

Here is a good article in the knowledge base about the use of boundary conditions.

https://kb.lumerical.com/en/ref_sim_obj_boundary_conditions_tab.html

Best Wishes,

Vivek


#3

Hi.
For the hexagonal, also in normal incidence, you must calculate both polarizations


#4

Hi,

For periodic structures, we suggest using the regular plane wave source with periodic (or Bloch boundaries for angled incidence, as mentioned by @vivek). You only need to simulate one unit cell and measure transmission and reflection; for example, if you get that the transmission at a certain wavelength is 25% it means that the reflection cross section is 25% of the unit cell area. This is discussed here.