Simulation of gold nanorod array

[Zhong Mei]

I’m using the FDTD 12 to simulation loacal surface plasmon resanance (LSPR) of gold nanorod array.

(1) How can I set the imput wavelength if I’m interested in the absorption/transmittance in the wavelength range of 400~1200 nm. I know i can set any specific wavelength at the imput plane panel, then what wavelength should i use and how do I set the other parametes like the bandwidth? I’m using the GMCW in which the panel only shows the time offset and the half width, how can i set that?
(2) when i use the FDA to export the result, it gives me a four-window panel. As i understand, it shows the power distribution, right? BUt what’s the difference of Real, Imaginary, Amplitude, Phase? and what are the meaning of Ex, Ey, Ez, Hx, Hy, Hz, Sy, Sy-x, Sy-z?

Sorry for so many questions.

[Damian Marek]

Hi,

1)There is a pretty good explanation of setting up the Gaussian Pulse at the following link:

Gaussian Pulse Description [FDTD]

Let me know if there are details you don’t understand.

2) Since the plots are based in the frequency domain and each plot is a single frequency, the fields are represented by phasors which are complex quantities. This link gives a brief description of what that means:

https://www.uic.edu/classes/eecs/eecs520/textbook/node35.html

The electric field is represented by the three different components (Ex, Ey, Ez) and the magnetic field is represented by (Hx, Hy, Hz). Finally, Sy is the calculated Poynting vector (directional energy flux density) in the y direction (normal to your observation area). The values Sy-x and Sy-z are the contributions of the Ex(Hz) and Ez(Hx) fields to the total Poynting vector.

Hope this clears things up!

[Zhong Mei]

Thank you very much, that makes sense!

Also, I dont known how to get the simulation result of the local electric field enhancement of gold nanorod array? As shown in the attached file (I found in a ref.), how do they get the value of E/E0?

[Damian Marek]

I found a paper that describes this calculation, you would need to do some post-processing of the field data on your own.

http://fy.chalmers.se/~klavs/papers/Nano_2006_field-enhance.pdf

You might also have to run a simulation with a simpler geometry as a kind of baseline to get the macroscopic applied field they talk about in the paper.

Regards

[Aurelien Duval]

Hi,

For now you can export the individual field component files (f3d files) from OptiFDTD analyzer and then process them in Matlab for example.

So, if you have an observation area recording the Ex, Ey and Ez components, after simulation, go to OptiFDTD analyzer in Tools-> Detector analyzis -> Observation Area. Then click on Export Data and select the Ex, Ey and Ez components.

You will have 3 files corresponding to Ex, Ey and Ez components. You can open these files in Matlab for example and do some calculations on them. For example:
E = sqrt(abs(Ex).^2 + abs(Ey).^2 +abs(Ez).^2)
This will give you the |E| value.

To obtain E0, run another simulation without your structure to make a reference and do the same.

From next release of OptiFDTD (latter this summer), we will provide a script function outputting the |E| value directly to file. You will also be able to perform calculations directly from the script editor in OptiFDTD.

Best regards

[Zhong Mei]

Damian and Aurelien,

Thank you very much for the kind reply! It is helpful, but still there is much work in the post processing, especially when I’m not very familiar with the Matlab. And it is difficult for me the show the total E in the colored strip format like what is shown in the reference. It will be better if the f3d file can show the total E in one file rather than Ex, Ey, Ez in three separate files.

[Aurelien Duval]

Hi,

You’ll be pleased to learn that the next update of OptiFDTD (12.1) will include this feature!
It will be available later this summer.

Aurelien

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