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Electromagnetic Waves, Axial Symmetry

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Can one specify a linearly polarized incoming (plane) wave for a geometry based on axial symmetry?
For instance if the incoming wave enters along the z-axis through a surface in the x-y plane . The polarization needs to be orthogonal to the z-axis. The only options are radial polarization and azimuthal (phi) polarization, and linear combinations. Neither represents the right physics - a linear polarized beam. (Radial polarization implies a line charge, azimuthal polarization a changing magnetic field in the z-direction).

Put another way - the linearly polarized field would break the axial symmetry; to represent a linear polarization as a sum of azimuthal and radial polarizations, the components must depend on the azimuthal coordinate (phi).

Is the only solution then a full three-dimensional geometry? We are hoping to avoid this.

3 Replies Last Post Mar 18, 2017, 7:07 p.m. EDT
Edgar J. Kaiser Certified Consultant

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Posted: 8 years ago Mar 16, 2017, 9:57 a.m. EDT
Gilad,

indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave.
2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry.
But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications.

Cheers
Edgar


--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Gilad, indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave. 2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry. But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com

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Posted: 8 years ago Mar 16, 2017, 8:49 p.m. EDT
COMSOL allows to specify the order in phi variation. Then in principle if the structure is cylindrically symmetric, the excitation can be expanded.


Gilad,

indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave.
2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry.
But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications.

Cheers
Edgar


--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com





--
Pu, ZHANG
DTU Fotonik
COMSOL allows to specify the order in phi variation. Then in principle if the structure is cylindrically symmetric, the excitation can be expanded. [QUOTE] Gilad, indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave. 2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry. But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com [/QUOTE] -- Pu, ZHANG DTU Fotonik

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Posted: 8 years ago Mar 18, 2017, 7:07 p.m. EDT
thanks!!!!!!
by the way,
does anybody know abou a comsol model of a photodiode?
i mean a tutorial or an example model?
thanks!!!!!! by the way, does anybody know abou a comsol model of a photodiode? i mean a tutorial or an example model?

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