- This topic has 9 replies, 2 voices, and was last updated 9 years ago by
Damian Marek.
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November 5, 2015 at 5:53 am #27452
Nathalie CarrierParticipantHi everyone,
I am using FDTD 12 (1 month evaluation) and I would like to create a new material in the FDTD profile designer based on experimental data.
These data are stored in a .txt file and contain 3 columns (wavelenght, index real part, index imaginary part). Is it possible to import them directly ?
Thanks for your help !
Nathalie -
November 6, 2015 at 8:57 am #27481
Damian Marek
ParticipantThe materials that are used in FDTD analysis MUST abide by the Kramers-Kronig relation. It is possible to fit the experimental data to a Lorentz drude model and then define a material with those coefficients. You can Matlab code from quick searches that will fit these problems.
http://fdtd.kintechlab.com/en/fitting
An example of a Matlab program can be found at the link.
Regards
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November 8, 2015 at 7:21 am #27538Nathalie CarrierParticipant
Hi Damian, thanks a lot for the reply, I will fit my data with a Lorentz Drude model.
\Nathalie -
November 18, 2015 at 11:38 am #27878Nathalie CarrierParticipant
Hello,
I am using the MatLab code that you provided me.
However fitting my data with ‘Lorentz Drude’ model appears not to be very accurate (see attached the best result I can get using 6 oscillators).
Would it be possible to import the data directly from XML format ?Thank you again,
\Nathalie-
November 19, 2015 at 10:11 am #27933Participant
Unfortunately no, the permittivity must be provided in Sellmeier, Lorentz, Drude or Lorentz Drude format for dispersive simulations. You could choose one wavelength you are interested in and run a CW simulation with a single sample of the data or maybe there is a matlab script out there that can perform a better fit.
Regards
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November 19, 2015 at 11:58 am #27947Nathalie CarrierParticipant
Thanks for the reply, I will focus more on the fitting then. It should be possible to find a better fit!
\Nathalie -
November 20, 2015 at 3:45 am #27963Nathalie CarrierParticipant
One last question, I tried to set a new material (with Sellmeier model) with the oscillator parameters I found (even if the fit is not perfect) but it seems that negative amplitudes are not supported. How to overcome that ?
I tried Lorentz-Drude, same issue.Thank you,
Nathalie-
November 30, 2015 at 10:05 am #28223Participant
The Lorentz-Drude model should allow negative strengths under the “S” parameter, I just verified that it works. It won’t work for Sellmeier model since it does not model loss. However, I am not sure what the physical meaning of a negative strength is!
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December 21, 2015 at 11:17 am #28853Nathalie CarrierParticipant
Hi thank you for the reply, I do not think there is a physical meaning of a negatig amplitude but the fit is good enough and in the Lorentz-Drude model form (and the fit does not converge with only positive amplitudes).
I still have a question regarding how to fit the permittivity. The convention used by the software is: a loss correspond to a negative imaginary part. For the example shown on the attached picture on the post from November 18, 2015 at 11:38 am, it means the imaginary part should be set as negative before fitting ?
Thank you,
Nathalie-
December 21, 2015 at 1:09 pm #28855Participant
Yes you should use the negative of the imaginary component and then do the fitting.
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January 21, 2016 at 6:44 am #29235
kasun gankanda
ParticipantHi
i am a new user to this software and is planning on using it for my research work.
currently i am making a simple simulation of SPR on a gold layer with a small slit on a glass surface .My problom is i cannot find how to make the glass material
and since i am planning to use Kretschmann cofiguration for SPR excitation .
what type of excitatio wave is good for the simulation.thank you in advance .
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