- This topic has 9 replies, 2 voices, and was last updated 8 years, 8 months ago by
Damian Marek.
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November 5, 2015 at 5:53 am #27452
Nathalie Carrier
ParticipantHi 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 #27538
Nathalie Carrier
ParticipantHi 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 #27878
Nathalie Carrier
ParticipantHello,
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 #27933
Damian Marek
ParticipantUnfortunately 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 #27947
Nathalie Carrier
ParticipantThanks 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 #27963
Nathalie Carrier
ParticipantOne 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 #28223
Damian Marek
ParticipantThe 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 #28853
Nathalie Carrier
ParticipantHi 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 #28855
Damian Marek
ParticipantYes 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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