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Scattering Boundary Conditions Giving Wavyness in Field for Reflectance Model

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Hello,

I am modeling both 2D and 3D planar surfaces and only the port boundary condition gives what seems to be the correct answer. Although, I do not want to simulate a waveguide. I thought the port b.c. is used for waveguides. I am not sure why, but the scattering boundary condition makes the solution wavy as if there are unwanted reflections. I want to move into non-planar surfaces and more in 3D but the scattering b.c. will be needed for these problems.

I have tried to implement perfectly matched layers, but I am doing it incorrectly. When they are not touching the original planar surfaces, the solution shows only green boxes as if no wave enter the solution area. When the P.M.L. are touching, a similar problem occurs. I may need to allow the wave to enter, but I do not know how to do that.

Thanks,
Brandon

2 Replies Last Post Nov 9, 2010, 1:28 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Nov 1, 2010, 2:04 a.m. EDT
Hi

do not forget you are solving field equations sow you should see the field changes with diffraction and scattering, these are not as smooth as one usually repesents ray tracing beams. But unwanted oscilaltions could also come from some numerical effects, difficult to say just like that in all generality

--
Good luck
Ivar
Hi do not forget you are solving field equations sow you should see the field changes with diffraction and scattering, these are not as smooth as one usually repesents ray tracing beams. But unwanted oscilaltions could also come from some numerical effects, difficult to say just like that in all generality -- Good luck Ivar

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Posted: 1 decade ago Nov 9, 2010, 1:28 p.m. EST
Thanks Ivar. I am just not completely positive that the 2D planar interface problem can be solved with scattering boundary conditions. It only gave decent answers with the port boundaries.

I also used the scattering bc with a matched at the backside. Can these two be used together? Or only a scattering bc with a scattering, and a matched boundary with a matched?

Also, my solutions, even for the port, gave negative reflectance. Is this possible?

Brandon
Thanks Ivar. I am just not completely positive that the 2D planar interface problem can be solved with scattering boundary conditions. It only gave decent answers with the port boundaries. I also used the scattering bc with a matched at the backside. Can these two be used together? Or only a scattering bc with a scattering, and a matched boundary with a matched? Also, my solutions, even for the port, gave negative reflectance. Is this possible? Brandon

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