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Questions for Mode Analysis Boundary Conditions

Posted 14.11.2024, 00:12 GMT-5 Wave Optics, Modeling Tools & Definitions, Physics Interfaces Version 6.2 2 Replies

Jason Huang
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Hello,

I'm currently using 2D Mode Analysis study to perform some optical mode analysis on a 2D waveguide, consisting of Lithium Niobate (core), SiO2 (substrate and cladding). I realize that if I set all boundaries to be "Scattering boundary conditions", the computed simulation field is very weekly confined in the waveguide region. However, if I change some boundaries to be "Perfectly Electrical Conductors", the field is confined within the waveguide very well. Intuitively the simulation I'm performing should be purely optical without any electrical contacts, which should not be affected by boundary conditions at all. Hence I wonder why the changes of boundary conditions will heavily impact the simulation field profile? Please feel free to let me know if there is anything I set incorrectly.

2 Replies Last Post 18.11.2024, 21:31 GMT-5
Arthur De Sousa
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Posted: 6 months ago 14.11.2024, 10:51 GMT-5

I checked your model and you actually don't even need to use the SBC. if you use the PEC on the boundaries of your geometry, it will also give you the right result. It allows to avoid diffusion and loss of your wave when you "introduce". Especially here, you don't have port so comsol does not understand the things like you if you don't put the right boundaries. At the end it is to mimic the a PEC but don't take it like a metal, it may be a bit weird but in case check the help or chatG*** he can explain quite well I hope it helps you

I checked your model and you actually don't even need to use the SBC. if you use the PEC on the boundaries of your geometry, it will also give you the right result. It allows to avoid diffusion and loss of your wave when you "introduce". Especially here, you don't have port so comsol does not understand the things like you if you don't put the right boundaries. At the end it is to mimic the a PEC but don't take it like a metal, it may be a bit weird but in case check the help or chatG*** he can explain quite well I hope it helps you
Jason Huang
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Posted: 6 months ago 18.11.2024, 21:31 GMT-5

Thank you for the response! I guess what I'm confused with is that it's not supposed to be Perfectly Electrical Conductors in my case. I wonder why the scattering boundary conditions are simply not working? Basically all of my materials are not supposed to be perfect conductors in which light is totally confined.

Thank you for the response! I guess what I'm confused with is that it's not supposed to be Perfectly Electrical Conductors in my case. I wonder why the scattering boundary conditions are simply not working? Basically all of my materials are not supposed to be perfect conductors in which light is totally confined.

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