- This topic has 19 replies, 3 voices, and was last updated 9 years, 11 months ago by
perveen akhter.
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May 21, 2014 at 10:36 am #11744
perveen akhter
ParticipantHi there,
I am working on this simple layout. it does work but simple Si 3.45 index is giving some oscillations at lower wavelengths and I have tried almost everything to fix this. but didn’t get it. can anyone please help me. -
May 28, 2014 at 11:03 am #11824
Aurelien Duval
ParticipantHi Perveen,
I’ve tried to run your example. However I don’t really anything wrong with it. Could you be more specific, for example a plot of the oscillations?
Thanks
Aurelien
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May 28, 2014 at 11:18 am #11825Participant
Thanks Aurelien for your reply.
the problem is that it doesn’t give a constant reflection,but with variations between 0.3 and 0.34 probably due to interference. so I was trying to get a more smoother reflection ,coz I plan to add metal nanoparticles on this subs and the plasmoinc effect is not as clear as it should be coz of this reflection interference. I am trying hard to find best APML no. of layers to minimize this.
I hope you got my question.
waiting for reply.
Perveen. -
May 28, 2014 at 11:32 am #11826Participant
Hi, with the project file you attached, I get 10^-18 W on the reflection observation area! It’s the computer’s way of saying 0.
Could you be more specific, for example giving a plot of the oscillations?Which version of OptiFDTD are you using?
Thank you
Aurelien
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May 28, 2014 at 12:01 pm #11827Participant
please find the attached reflection plot. I want to get a smooth/constant reflecion.
we have version 9.
thanks,
Perveen. -
May 28, 2014 at 12:31 pm #11830Participant
Ok, I understand better, thank you.
You should increase the number of PML layers to absorb more incoming light. For example with 64 layers, almost all oscillations are gone.
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May 28, 2014 at 2:16 pm #11831Participant
did you change anything else too. coz I am still getting the same results. also I am using APML boundary conditions, not PML?
and no. of APML layer coefficients is 30.
any suggestions?
thanks. -
June 2, 2014 at 1:23 pm #11867Participant
I cannot easily tell you if the inner workings or the simulation engine changed for that particular point between version 9 and 12.
Like I said, the more layers, the less reflections you will get, but the slowest the simulation will run. -
June 17, 2014 at 10:11 am #12054Participant
Hi there,
it seems that for a layout which is working fine, changing xy wafer dimestions changes the results a lot, keeping same mesh size and even increasing the timesteps doesn’t produce the same restuls as original layout. how to compensate the wafer size effects?
thanks. -
November 10, 2014 at 9:44 am #15140Participant
Hi there,
it seems that for a layout which is working fine, changing xy wafer dimestions changes the results a lot, keeping same mesh size and even increasing the timesteps doesn’t produce the same restuls as original layout. how to compensate the wafer size effects?
thanks. -
November 10, 2014 at 11:07 am #15142
Damian Marek
ParticipantDo you have a more recent project file? I could take a look.
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November 10, 2014 at 11:52 am #15145Participant
please find the attached layout and the results. I started with gold np sample# 52 and change the size n getting a lot of noisy peaks.
thanks,
Perveen.-
November 10, 2014 at 1:46 pm #15152Participant
Ah, the first thing I notice is that you are using periodic boundary conditions for the x and y dimensions. When you modify the x and y; lengths you are effectively changing your periodic lattice, or the distance between nano-particles.
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November 10, 2014 at 2:06 pm #15153Participant
so bigger wafer size, means larger distance betweeen particles, so no interaction, so I should get better results. but doesn’t work that way.
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November 10, 2014 at 4:06 pm #15161Participant
Are you trying to simulate a periodic structure? If not I would suggest simply using absorbing boundary conditions on all boundaries and use a Gaussian spatial input instead of the rectangular.
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November 11, 2014 at 8:07 am #15196Participant
thanks, if you can send me a layout. or modify my layou n send to me. I am using version 9. thanks a lot.
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January 7, 2015 at 10:44 am #17095Participant
Hi Damien,
I need your help with this layout simple thin film on si substrate with input at 45 deg. for some reasons I am getting negative absorption.
attached is the layout and plot.
thanks,
Perveen. -
January 7, 2015 at 4:03 pm #17120Participant
Hi Perveen,
The silicon carbide material is defined with a positive imaginary part of the index of refraction. In engineering convention (and OptiFDTD convention) this means an amplifying medium, not a lossy one. You may want to change that to a negative imaginary part. This amplifying effect is what I assume is giving you a negative absorption.
Regards
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January 7, 2015 at 7:15 pm #17124Participant
still getting negative absorption. could this be coming from any interference coz of input angle being 45 deg????
thanks,
Perveen.
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November 10, 2014 at 12:55 pm #15151Participant
first slide is for radius50 nm, second for 10 nm
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