FDTD simulation validity

[Chao Zhang]

Hi

I am recently doing some EM simulation in the terahertz range. However, I am not very clear whether FDTD method is valid to do this job. So anyone can reply to me that if the FDTD product of Optiwave is able to do that. I know that this method is very popular in nanophotonics research. Terahertz structure should be much larger than the nano field. Thanks

[Luis Acevedo]

FDTD works ok in um and nm fields
GHz is ok

You can try to simulate something in OptiFDTD with this units.

[Luis Acevedo]

You should be ok in Terahertz, BUT, a big But
You must analyse an um or nm structure in nearfield
Try out a preliminary model

[Aurelien Duval]

It should be doable if you do not use predefined materials (such as metals etc) since they are defined in the visible-NIR range usually.
The best way to ensure that is to try out our software. If you are ensure on what to do, simply post a link to a reference article and we’ll see if we can reproduce the results.

[Luis Acevedo]

yeah thanks for the note

[Azzouz Sellai]

Hi
Has anyone developed a FDTD simulation of a simple Otto or Kretschmann configurations for surface plasmons excitations? I am learning to use FDTD which seems quite different from COMSOL!

[Aurelien Duval]

Hi,

Here’s a pretty basic example.

I use a SF10 glass prism to couple into a 50 nm thick layer of gold. The analyte is water at 1.33 and the wavelength is 633 nm.
You’ll notice that the coupling conditions are not perfectly met, probably due to a slight change in refractive index of gold as compared to the source I used to determine the angle (57 degrees incidence from the vertical).

What is important for this type of simulations is to mesh fine enough to resolve correctly the metallic layer (here I go down to 5 nm resolution, but it’s probably overkill).

A note: performances will be horrible compared to simple analytical formulations (Fresnel reflection coefficients and Rouard method for example). It only makes sense if you geometry is not a simple uniform film.

Attachments:

1. prismKretschmann.fdt

[Duane Kaufman]

Hello,

My name is Duane Kaufman, and I am trying to teach myself the tools of Surface Plasmon Resonance detection.
I have downloaded the free 32-bit version of OptiFDTD to familiarize myself.

The prismKretschmann.fdt file posted on this thread would be a great start for me to get my feet wet, but my version of OptiFDTD cannot open this file (prismKretschmann.fdt cannot be opened. It was created with a newer version of OptiFDTD)

Would it be possible to create this example in a format the 32-bit version could open?

Your help is appreciated!
Duane

[Damian Marek]

Hi Duane,

Try this file.

Regards

Attachments:

1. Prism32BIT.fdt

[Duane Kaufman]

Hello,

Thanks for the file, it loads properly.

Now I need to learn what I can!

Duane

[Luis Acevedo]

Thanks for the example. I am learning a lot with you feedback.

[Sourabh Sahu]

is it possible to simulate micro toroid and mico ring resonator using OptiFDTD

[Damian Marek]

Undoubtedly, we have a very common example of a micro ring resonator that comes in the samples folder in your installation directory. Using a ring waveguide with a fiber profile the toroid structure can be made in exactly the same way.

Cheers

[Noha Anous]

Dear Damian,
Thanks for the prism file comaptible with the 32 bits,
but I have some questions if you please:

1 – To compute the effective index of the structure, shall I choose 2D modal, then when computing the mode, shall I click on the 3 waveguides?? or only the gold to compute the plasmonic mode?
(When I choose the three waveguide, I do not get a mode)

2- On the other hand, only choosing the gold layer, gives me only 1 symmetrical mode … there is supposed to be another antisymmetrical mode which doesn’t appear even when I increase the no. of modes to be computed!

3 – How is it possible to increase the resolution in the modal solutions?? It is set to 401 points, is it possible I’m not getting the anti-symmetrical mode because of the low resolution?

4- As for the ring example you mentioned earlier, it’s a dielectric ring, is there an example for a plasmonic ring because I’m facing some problems with that?

Thanks a lot in advance.

Noha

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