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Photonic Bandgap Analysis for Lossy Materials

Posted 28.11.2017, 07:11 GMT-5 Wave Optics 2 Replies

Ali Keçebaş
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Hi

I want to calculate photonic bandgap of a 2D photonic crystal of a lossy, dispersive structure at the wavelengths of interests. I came across the tutorial (application ID:798), but an unlossy material is simulated (k=0).

Can COMSOL calculate the photonic bandgap of a lossy structure at a similar manner?

Thanks

2 Replies Last Post 27.09.2018, 09:30 GMT-4
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Hello Ali Keçebaş

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Adrien Dousse
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Posted: 6 years ago 27.03.2018, 12:41 GMT-4

Hello Ali Keçebaş I am also trying to simulate a photonic crystal bandgap using lossy material. In the tutorial model (ID:798), when using a finite value for the extinction coefficient (k=0.5 for example, ie a constant with respect to frequency), study 2 does not converge. However study 1 does. Try and put a parameter sweep in study 1 for the k value. The solutions obtained by study 1 are the same as the ones obtained from study 2, however, complex valued refractive index can be used as well ! The drawback is that the eigenfrequencies are not always nicely ordered in bands, the solver might jump from band to band. I havent figured out how to make study 2 converge with complex valued refractive indices, have you found a solution ?

Hello Ali Keçebaş I am also trying to simulate a photonic crystal bandgap using lossy material. In the tutorial model (ID:798), when using a finite value for the extinction coefficient (k=0.5 for example, ie a constant with respect to frequency), study 2 does not converge. However study 1 does. Try and put a parameter sweep in study 1 for the k value. The solutions obtained by study 1 are the same as the ones obtained from study 2, however, complex valued refractive index can be used as well ! The drawback is that the eigenfrequencies are not always nicely ordered in bands, the solver might jump from band to band. I havent figured out how to make study 2 converge with complex valued refractive indices, have you found a solution ?
Ali Keçebaş
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Posted: 6 years ago 27.09.2018, 09:30 GMT-4

Dear Adrien,

I turned back to the problem just today and saw your response. ' when using a finite value for the extinction coefficient (k=0.5 for example, ie a constant with respect to frequency), study 2 does not converge. However study 1 does. ' I got the same with you but I do not understand the following: 'Try and put a parameter sweep in study 1 for the k value. The solutions obtained by study 1 are the same as the ones obtained from study 2, however, complex valued refractive index can be used as well !' You said that study two does not converge. Did you mean that even if you changed 'k' you got the same results in study 1. Because that is what I observed. Since study two does not converge, I would not be able to get band diagrams for the modes.

Although I am not an expert on the subject, maybe some additional changes are required to include loss other than just changing the value of 'k'. Because it does not seem to change anything.

Dear Adrien, I turned back to the problem just today and saw your response. ' when using a finite value for the extinction coefficient (k=0.5 for example, ie a constant with respect to frequency), study 2 does not converge. However study 1 does. ' I got the same with you but I do not understand the following: 'Try and put a parameter sweep in study 1 for the k value. The solutions obtained by study 1 are the same as the ones obtained from study 2, however, complex valued refractive index can be used as well !' You said that study two does not converge. Did you mean that even if you changed 'k' you got the same results in study 1. Because that is what I observed. Since study two does not converge, I would not be able to get band diagrams for the modes. Although I am not an expert on the subject, maybe some additional changes are required to include loss other than just changing the value of 'k'. Because it does not seem to change anything.

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