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Fundamental mode of PCF not found
Posted Apr 1, 2017, 7:50 p.m. EDT RF & Microwave Engineering, Wave Optics, Studies & Solvers Version 5.1 2 Replies
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Hi,
I try really hard to make my COMSOL find the fundamental mode of a solid-core photonic crystal fiber, but without any success. I use mode analysis and tell COMSOL to look around the refractive index of the glass. Every time I get some 'mode' at the boundary with the PML (see attached picture), but not in the core. I tried separating fiber and PML with some air (material of the PML always the same as the one it borders with) but it did not help. Only without the outer part of the cladding and the PML I can get nicely looking mode in the core.
I need to search only for two modes and be sure I have the x and y polarizations of the fundamental mode as a result.
Any help to get the fundamental mode keeping the PML and proper fiber structure would be appreciated.
Thanks in advance,
Adam
I try really hard to make my COMSOL find the fundamental mode of a solid-core photonic crystal fiber, but without any success. I use mode analysis and tell COMSOL to look around the refractive index of the glass. Every time I get some 'mode' at the boundary with the PML (see attached picture), but not in the core. I tried separating fiber and PML with some air (material of the PML always the same as the one it borders with) but it did not help. Only without the outer part of the cladding and the PML I can get nicely looking mode in the core.
I need to search only for two modes and be sure I have the x and y polarizations of the fundamental mode as a result.
Any help to get the fundamental mode keeping the PML and proper fiber structure would be appreciated.
Thanks in advance,
Adam
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2 Replies Last Post Apr 3, 2017, 2:05 p.m. EDT
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Posted:
7 years ago
I assume you are using BOUNDARY mode analysis. You can choose to have Comsol search in a region defined by the effective mode index or the wavenumber in the direction of propagation. The effective mode index is the ratio between the wave propagation velocity and the speed of light. That is: it is less than unity and NOT the same as the index of refraction. Indeed, the effective mode index of the fundamental mode is usually close to the reciprocal of the index of refraction.
D.W. Greve
DWGreve Consulting
D.W. Greve
DWGreve Consulting
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Posted:
7 years ago
Thank You for the reply.
No, I'm using simple Mode Analysis as it is used in the example for step-index fiber and by others trying to model PCFs (I'm a newbie to COMSOL). I have no idea how to use Boundary Mode Analysis, especially "Ports".
Effective refractive index tells how many times slower the wave is propagating in the medium than in the vacuum. This approach works for step-index fibers as well as for my structure without cladding and PML.
Best regards,
Adam
No, I'm using simple Mode Analysis as it is used in the example for step-index fiber and by others trying to model PCFs (I'm a newbie to COMSOL). I have no idea how to use Boundary Mode Analysis, especially "Ports".
Effective refractive index tells how many times slower the wave is propagating in the medium than in the vacuum. This approach works for step-index fibers as well as for my structure without cladding and PML.
Best regards,
Adam