Learning Forum

[ejlee0911]

Hello. I simulated the Fabry-Perot cavity in which a dipole source exists. To get transmission results, Trans_box ( considering only +z flux) and 2D Z normal monitor were used.

[ejlee0911]

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[ejlee0911]

Monitor located at the top in total simulation is the monitor where I got the "sourcepower/dipolepower".
Using the transmission box surrounded dipole source, I wonder if it's the right way to get the sourcepower through the monitor at the top and calculate dipolepower.
I look forward to your reply. Thank you.

[ejlee0911]

When the length of the dielectric medium is satisfied with constructive interference condition (L = m*(lambda/2)), the oscillating region mentioned above exists only in the lossless dielectric medium.
Is it possible to use dipolepower command, different from the case mentioned above?
Thanks for your help.

[Guilin Sun]

There are several related issues that need to be clarified:
sourcepower is analytical without considering the environment and material loss, eg, it is analytically calculated as if the dipole is located in a homogeneous lossless medium.
dipolepower is the actual radiated power, provided that the dipole is located in lossless, or with small dispersion, and the mesh size is not very small.
Please refer: dipolepower - Script command sourcepower - Script command
The transmission from the monitor is T_mon=recorded_power/sourcepower, and the renormalization should be T+T_mon*sourcepower/dipolepower as you did.
However, since it has strict conditions to use dipolepower, you may need to use a box monitor group to get the radiated power. The accuracy of this method depends on the box volume (as it needs spatial integration), the box size and loss of the material involved. It can underestimate the radiated power if the box is large and the loss is strong, as some power can be absorbed inside the box.
As for the result you provided:

the renormalized is smaller than 1 (the dash curve), which indicates the dipolepower may be accurate.
The grey box around the dipole is used for source injection. Inside the box the fields are not physical. So as long as your monitor does not penetrate this region, it should be ok. If you find the result is not reasonable, then we can take a close look.