[Nathalie 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

[Nathalie 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

[Nathalie CarrierParticipant]

Thanks for the reply, I will focus more on the fitting then. It should be possible to find a better fit!
\Nathalie

[Nathalie 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

[Nathalie CarrierParticipant]

About how to tilt the input plane I found the answer on the forum !
\Nathalie

[Nathalie CarrierParticipant]

Damian, thank you for the reply, it helped me a lot ! You are right for the structure and I finaly did not use the PBG structure at all. Can I ask for 3 more questions about structure design ?

I want to simulate surface plasmons in a thin Ag layer (~40 nm thick) deposited on glass. The layer is perforated with a 2D array of circular air holes (close packed lattice, with lattice parameter 0.562nm). Light is propagating through the glass, the perforated Ag layer and then the air medium.

– I chose the simulation domain to be glass (n=1.5).
– I adjusted the simulation domain dimensions in order that it matches with the unit cell of my structure and used periodic boundaries conditions.
– I created a linear waveguide of silver (40 nm thick).
– I created cylinders made of air, their centers are separated by the pitch (562 nm).
– I created a linear waveguide of air.

I put in attached the final design, could you take a look at it ? I have two issues about it.

First, I wonder what would be the difference between a 3D block of Ag and the linear waveguide profile used ?
Then, some cylinders are not entirely in the simulation domain in order to define the unit cell, is that a problem ?
Finaly, I wish to study the structure not only at normal incidence but with an angle, how is that possible ? By tilting the imput plane or the structure (then I will have issues with the periodic conditions to define the 2D array…)

It would really help me if you had some piece of advice,
Thank you a lot !
Nathalie

[Nathalie CarrierParticipant]

Hi Damian, thanks a lot for the reply, I will fit my data with a Lorentz Drude model.
\Nathalie