Complete EM Field of Gaussian Beam: References & Pointers

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Discussion Overview

The discussion centers around the complete electromagnetic field of a Gaussian beam, specifically seeking references and formulas for the components Ex, Ey, and Ez. The context includes theoretical aspects of Gaussian beams as they relate to laser profiles and their mathematical representations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests references for the complete electromagnetic field of a Gaussian beam, noting the Gaussian profile in the x-y plane and questioning the implications of the divergence condition on Ez.
  • Another participant suggests that the exact formulas for Ex, Ey, and Ez correspond to separable Helmholtz equations and that Gaussian beams can be represented as superpositions of plane waves, implying that Ez could be non-zero.
  • A reference to a book by Yariv titled "Quantum Electronics" is provided as a potential source of information on the topic.
  • One participant notes that Gaussian beams are favored for their straightforward Fourier Transform properties.
  • A participant mentions the complexity of the full vector representation of Gaussian beams and cites a specific journal article that discusses vector Gaussian beam propagation beyond the paraxial approximation, indicating that a simpler vector solution may exist.
  • Another participant expresses concern about the complexity of the topic and shares an additional reference related to Helmholtz equations, although they acknowledge it may not directly address the original question.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and access to resources, with some agreeing on the complexity of the topic while others provide different references and approaches. No consensus on the exact formulas or representations exists.

Contextual Notes

Participants highlight the complexity of the full vector representation and the potential limitations of existing references. There is an acknowledgment of the need for specific boundary conditions and the implications of the paraxial approximation.

pervect
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Does anyone have any references or pointers to the complete electromagnetic field of a "Gaussian Beam"?

By Gaussian, I mean that for a beam propagating in the z direction, a cross-section of the beam in the x-yplane has

|E| = k exp( -(x^2+y^2)/w^2 )

see for instance
http://en.wikipedia.org/wiki/Gaussian_beam

I gather that real laser beams tend to have this sort of "Gaussian" profile. However, I haven't been able to find out anything with exact formulas for Ex, Ey, and Ez. [itex]\nabla \cdot E = 0[/itex] seems to imply that Ez is not zero.
 
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Actually,the exact formulas for Ex,Ey,Ez are the same as separable Helmholtz eqations in Cartesian coordinates. The Gaussian packet(beam) form is just a kind of B.C. You can simply superpose plane waves(in coordinate) to get a Gaussian shape. In this sense, kx,ky are generally non-zero,so Ez could also be non-zero. It´s not a problem though, since this is not plane wave at all.
 
There is a book by Yariv..Quantum Electronics.Wiley 1967
I guess you should find good stuff there.

Best Regards,

DaTario
 
Note that one of the reasons for Gaussian to be used is its easy doing Fourier Transform (spectrum)
 
The full vector representation is disgustingly complicated :smile: .

I was only able to find the vector representation in an optics journal, the reference is;

'Analysis of vector Gaussian beam propagation and the validity of paraxial and spherical approximations.' Carl G. Chen, Paul T. Konkola, Juan Ferrera, Ralf K. Heilmann, Mark L. Schattenburg, JOSA A, Volume 19, Issue 2, 404-412, (2002).

You won't be able to access it though unless your institution has a subsciption with the OSA.

On the paper, I noticed that it goes beyond the Paraxial approximation, a vector solution including the paraxial approximation may be less complicated.

Claude.
 
Claude Bile said:
The full vector representation is disgustingly complicated :smile: .

Heh - I was afraid of that, thanks.

I was only able to find the vector representation in an optics journal, the reference is;

'Analysis of vector Gaussian beam propagation and the validity of paraxial and spherical approximations.' Carl G. Chen, Paul T. Konkola, Juan Ferrera, Ralf K. Heilmann, Mark L. Schattenburg, JOSA A, Volume 19, Issue 2, 404-412, (2002).

I don't have access to that paper, unfortunately, but I did find an interesting reference online when I included "Helmholtz" in my keywords

http://www.hep.princeton.edu/~mcdonald/examples/oblate_wave.pdf

I don't think this paper directly answers my question, but it does give me an idea of how messy the problem is :-)
 

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