Difference in proof between TE and TM modes

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SUMMARY

The discussion focuses on the mathematical differences between Transverse Electric (TE) and Transverse Magnetic (TM) modes in waveguide theory. The TE modes are characterized by the equations Ey(x, z, t) = Em(x) = exp[i(ωt-βz)], leading to symmetric and asymmetric solutions defined by ptan(pd/2) = q and pcot(pd/2) = -q, respectively. In contrast, TM modes introduce the dielectric constant into the eigen equations, affecting the solutions but maintaining similar mathematical structures. The user seeks clarification on how the dielectric constant alters the TM mode solutions compared to TE modes.

PREREQUISITES
  • Understanding of waveguide theory and modes
  • Familiarity with mathematical functions such as sine, cosine, and exponential
  • Knowledge of dielectric constants and their role in electromagnetic theory
  • Basic grasp of eigenvalue problems in physics
NEXT STEPS
  • Study the derivation of TM mode solutions in slab waveguides, focusing on the impact of dielectric constants
  • Learn about eigenvalue equations in electromagnetic wave propagation
  • Explore the mathematical differences between TE and TM modes in various waveguide configurations
  • Review the principles of electromagnetic field theory, particularly in relation to waveguide applications
USEFUL FOR

Students and professionals in electrical engineering, particularly those specializing in waveguide design, electromagnetic theory, and optical communications.

GengisKhan
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I'm a little confused regarding the maths of TE and TM modes.

Solving the following system for TE (which derives from Ey(x, z, t) = Em(x) = exp[i(ωt-βz)] ):
Asin(px) + Bcos(px) , -d/2 < x <d/2
Cexp(-qx), x>d/2
Dexp(qx), x<-d/2

we conclude in two types of solutions for TE modes: symmetric: ptan(pd/2) = q and asymmetric: pcot(pd/2) = -q.

What is different for the above solutions for TM? I have a hard time determining that. I think it has something to do with the dielectric constant, but I'm not quite sure.

I can elaborate on any maths you ask for. Also sorry for the quality of my post, it is my first one.
 
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Hi, when you write the solution Ey =exp[i(\omega t - \beta z)], this is a wave traveling in the negative z direction.

If you want to break this wave as the sum of a TE mode and a TM mode, then for the TE wave, only Ez is 0. Ex, Ey, Hx, Hy, and Hz are not zero. for the TM wave, Hz is 0. Ex, Ey, Ez, Hx, Hy are not zero.

I cannot relate your question to the definitions of the TE and TM mode.

elgen
 
Elgen, thanks for your answer! That's the very first part of the proof, I'm trying to understand beyond that.
Fortunately, I found some insight from http://ece562web.groups.et.byu.net/notes/slab_waveguide.pdf.
TM Modes solutions are found at pages 8-9. The problem is that I don't know how to reach the eigen equations, which are the same as TE's (described earlier in the .pdf), only with the dielectric constant n^2 added. If someone can briefly describe what is different from TE, I'd be grateful!
 

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