E field profile of an array of nanoparticles

fdtd
periodic

#1

I would like to have the E field profile for an array of nanoparticles…TO do this I make two files where the difference is the chice of the simulation region 1. I have chosen one unit cell
the other mor ethan one
1.fsp (265.9 KB)
2.fsp (263.5 KB)
when i try to plot the field profiles they em to be lot different…
Is my positioning of the of th monitor correct?
there can be a difference in the transmittance ata as the particle are not same…
i would like to have the ame E field plot as that of 2…


Transmission for finite number of cells
#2

@tapajyoti_das_gupta:

Hi. I noticed that the two simulation files you attached are quite different. Some of the differences I noticed are the following:

  • Size of the nanosquares: 0.21x0.21um in file 1.fsp, 0.165x0.165um in file 2.fsp
  • Substrate and film materials are different.

Furthermore, the FDTD simulation region size and position in both simulations need to be corrected assuming that you want a periodic array of squares with period 0.35um in the x and y directions. In 1.fsp the span of the FDTD region should be three times the period, that is 3x0.35um=1.05um, but the span you have is 1um. In 2.fsp the position and size of the FDTD region lead to a very different structure, as you can see in the image below:

Take a look at the attached files 1_modified.fsp (258.7 KB) and 3.fsp (257.6 KB) where I used the structure in 1.fsp as starting point. Note that in both cases the results from the field monitors are equivalent, as expected, since the only difference is the choice of the unit cell. To save simulation time you should always use the minimal cell for simulating periodic structures.

Note some important points:

  1. I made sure the monitors for reflection and transmission cover the entire simulation region.
  2. I increased the size of the FDTD region in the z direction to make sure the distance from the array to the PML is at least half the maximum wavelength.
  3. Used “steep angle” PML; you can read more about this choice in this posting.
  4. Use symmetric and antisymmetric boundary conditions to save simulation time.
  5. Improved the material fit for the polymer material reducing the “fit Tolerance” and increasing the “imaginary weight” as explained here. You can check the new material fit in the Material Explorer.
  6. Increased the simulation time so that the fields have enough time to leave the simulation region.
  7. Used a mesh override region to make sure each nanosquare was meshed in the same way.

For more examples about how to choose the unit cell for simulations with periodic structures you can also look at this posting.