Problems introducing a defect in my design

[davcm]

Hello,
I am working in Photonic Crystals. My structure is a row of air cylinders in silica. When I run the PWE band solver parameters all seems to go correctly. But when I try to introduce a deffect and again run the PWE band solver, theres is no difference (and it should). For introducing my deffect I go to Crystal Lattice properties and then I select the third cell (0 0 2) and edit its parameters (if just want to change a little bit its radius) or turn the cell off. But, as I said before, when I run the PWE, nothing happens.

I attach the project file.

Thanks a lot.

David.

Attachments:

1. cilindros_air_wafer_air1.fdt

[davcm]

Hello,
Finally I could. I only had to change the supercell value. But there is still something strange: if I simulate without the deffect the structure with a supercell of 1×1 the band diagram is different than the one obtained using more supercells (for example 1×10). Why is that? The bandgap is supposed not to change if the cylinders are the same. Should have only a computational cost … isn’t it?

Thanks,
David

[Damian Marek]

The problem here is that you need to define the supercell to include your defect (and the rest of the structure). The default supercell is only a single element, so in your case it would be the first rod from the left. Go to Simulation->PWE Band Solver Parameters and change the Supercells from #c = 1 to #c = 20.

That should do the trick!

[davcm]

Thanks Damian for answering to me so quick. I realized what you told me (in fact I worte a message to you 8 minutes before your response saying this :)) but the thing now is that I don’t understand that, if I run the simulation without any deffect the band diagram is different depending on the supercell I choose. I am not very sure, but if I have a regular and symetric system, simulating with 1×1 supercells or 1×20 should give me the same band diagram. And I don’t know why it is not like this…

Thanks Damian!

[Damian Marek]

Good catch, do you have a scientific article you are trying to reproduce? It helps us determine how to fix the project file and which results we should be matching.

[davcm]

Hello Damian,
I am not trying to reproduce any particular scintifica article but guess there is bicliography talking about it. I am going to search and if I find something interesting, I pass it to you.

Regards.

DCM

[Dr. Subhashish Tiwari]

Hey davcm,

The answer to your question is , the band gap will not change without or with introducing defect/s.

Since the bandgap obtained at first is the base to proceed further , to introduce custom defects.

Thanks

[Sourabh Sahu]

Hi davcm,

Band gap only changes when you make significant change in hole structures i.e. either increase or decrease dielectric constants of holes. When you increase the dielectric constant propagation vectors in PWE expansion moves down and vice versa.

Attachments:

1. 

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[Ravil]

Hi Sourabh, when you elaborating about the change in a band structure, you mean that you do it by changing the material itself, i.e. producing QW, QD, etc.? You can’t change the structure of holes, can you?

[Ravil]

According to your original question, did you try to simulate your project in any other environment?

[Sourabh Sahu]

hey ravil

by changing material we can modulate band gap in photonic crystal structures. modification in holes dimesion (i.e. circular or elliptical) also effect band gap

[Author]

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