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Question

POP - Beam propogation data as ZBF in text format

  • 24 May 2024
  • 1 reply
  • 96 views

I am going through the article on POP analysis, and came across this : 

“Under the Display tab, check Save Output Beam To: and Save Beam At All Surfaces. These options create a Zemax Beam (.zbf) File at every surface that contains the electric field information.”

Here is the aricle : https://support.zemax.com/hc/en-us/articles/1500005488601-Using-Physical-Optics-Propagation-POP-Part-1-Inspecting-the-beams

The ZBF file output seems to give only irradiance in watts/mm^2. There is an option called Ex and Ey irradiance, not sure what this means, but it seems like irradiance output in either x or y coordinate.

I understand that it is the electric field (complex) that is being propogated in free space with POP algorithm, but the output is always irradiance, right?

Is it possible to retrieve the electric field data by sq root of irradiance ? I am trying to get some clarity on whether the ZBF text file has irradiance or electric field data ? 

Any help would be very much appreciated. 

Regards, 

NC

 

 

1 reply

Jeff.Wilde
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The ZBF file contains electric field data.  If scalar diffraction is sufficient, so that polarization ray tracing is not needed, then the ZBF file contains one complex field (scalar) value per point in the mesh.  The format is (real, imaginary), but this can be easily converted into (mag, phase) once the ZBF file is transferred to, say, Matlab.

If polarization is needed, then this option can be selected in POP:

 

In either case, the field data is contained in both the binary and text versions of the ZBF file:

 

 

Note the last line in the red box above:  the local beam power at any point in the mesh = |Ex|^2 + |Ey|^2.  The local irradiance should then simply be the power of the mesh pixel divided by the area of the pixel.  Alternatively, the local phase of the beam at any mesh pixel can be displayed based on real and imaginary parts of each field component individually, or the sum (i.e., the total field).   Again, for non-polarized (scalar) simulation, only the Ex component is utilized (as a placeholder for the scalar field, which should not be interpreted to mean the field is x-polarized).

Regards,

Jeff

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