Fresnel Equations Simulation in 2D: How to Avoid Side Entry in Comsol?

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SUMMARY

The forum discussion centers on simulating Fresnel equations in 2D using COMSOL Multiphysics. The user encountered discrepancies in reflectance and transmission values for TE and TM waves at larger angles of incidence, suspecting side entry of electromagnetic waves due to incorrect boundary conditions. The issue was resolved by adjusting the propagation constant of the ports to ensure it corresponds to the vertical component of the wave vector with a positive sign, facilitating correct wave propagation in the desired direction.

PREREQUISITES
  • COMSOL Multiphysics 5.6 or later
  • Understanding of Fresnel equations
  • Knowledge of TE and TM wave polarization
  • Familiarity with boundary conditions in electromagnetic simulations
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  • Research "COMSOL Multiphysics propagation constant settings"
  • Study "Fresnel equations for TE and TM waves"
  • Learn about "Floquet periodic boundary conditions in COMSOL"
  • Explore "Electromagnetic wave propagation in dielectric materials"
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This discussion is beneficial for physicists, electrical engineers, and simulation specialists working with electromagnetic wave propagation and COMSOL Multiphysics, particularly those focusing on optical simulations and boundary condition management.

MarcelComsol
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Hi there,

I'm failing in simulating the fresnel equations in 2D with Comsol.

As you can see in the model added to this post, the reflectance and transmission in the global plots both for TE-waves ("Port, senkrecht polarisiert", Plot "Reflektion und Transimission, senkrecht") and TM-waves ("Port, parallel poralisiert", Plot "Reflektion und Transmission, paralell") seems to be correct for small angles of alpha. But for bigger angles of alpha, the simulated values differ strongly from the analytical solutions. I suspect that the wave from the upper port is also entering from the sides of the dielectrica (side 1 and 6), since we have also an electrical field in the dielectrica for alpha equals 90 degrees(see picture below). How can I avoid the electromagnetic wave entering from the sides 1 and 6 (i chose floquet periodic boundary conditions)?

upload_2019-3-19_8-20-12.png

Picture above: TM waves, alpha=90 degrees, but still a wave is entering my dielectrica(the lower half)

I would be very happy about every help in this problem!
Best wishes

model: https://drive.google.com/open?id=107LINBOhmZtR_uzkJhYKgNb8POFVLMX6
 

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I was able to solve the problem in the meantime :-)
 
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MarcelComsol said:
I was able to solve the problem in the meantime :-)
Can you tell us how you did it?
 
Hi DrClaude

The problem was the propagation constant of my ports...

My current understanding of the propagation constant is that it must correspond to the vertical component of the wave vector. It must also have a positive sign, otherwise the wave will propagate upwards.
(Provided that the wave should propagate in the negative y-axis and the coordinate system is defined that the y-axis points upwards)
 
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