Learning Forum

[di.chang]

Hi All,

I would like to ask two separate questions here:

1. I ran the same POP.zmx file on two computers that have the same version of Zemax version, 2023.R2.02. System settings and POP settings are all the same. One gives fiber coupling efficiency 72% and the other one gives 80%. What could be the reasons behind this discrepancy?
2. I ran that POP.zmx file on one computer that has Zemax version 2024.R2.02. It’s a simple optical system using two lenses collimating and coupling laser coming out from one fiber into the other one. I have a dummy surface before the first lens to check the beam. In the Physical Optics option under Surface properties, if I turned off “Auto Resample”, it gives coupling efficiency of 93% and a 10E+04 times higher total power (while the input is 1.0). However, if I turned on “Auto Resample”, it gives coupling efficiency of 77% and a 0.99 total power (more reasonable). My questions is: why sampling affects the fiber coupling efficiency calculation and which value is more trustable?

       Following above, I ran the same POP.zmx file on one computer that has Zemax version 2023.R2.02. Resampling on that same surface                       does not change the coupling result. My question is: What is the difference between the sampling of 2023.R2 and 2024.R2?

• Here are some specific examples to illustrate how the sampling choice affecting the total power calculation:

        As we change the sampling on dummy surface #1, which is just a standard surface sitting in front of all lenses. Beam propagates from source to this surface without anything in between. Here are some results using Zemax 2024.R2.02:

• When resampling is completely off: Total power is 1, which is desired.

 

• When “Auto resample” is clicked: Total power drops to 0.2, which is not right.

 

• When I reduced the X-width and Y-width, i.e., the window size while keep the sampling number the same: Total power increases to 1.7, which does not make sense because there is clipping now.

 

• When I try to over sample it with original grid size by increasing the sampling number, total power increases to 3.9. This is to say the higher the resolution, the higher the total power is.

 

• When I try to under sample it with original grid size by decreasing the sampling number, total power decreases significantly to 0.06. This is to say the lower the resolution, the lower the total power is.

Is this possibly a BUG in Zemax POP calculation?

The version 2024.R1 also has bug: changing sampling does not change total power at all. It remains 1.

With a big grid size 2 x 2

With a small grid size 0.1 x 0.1 so the beam is highly clipped, how come the total power is still 1?

 

Thank you!

Di

[Niki Papachristou]

Hi Di,

Thank you for reaching out to us, and reporting your findings. However, there are several reasons for these to be occured within POP tool before we conclude that this is a bug. One example is that the POP settings are different for different cases, also make sure that you click save button before the calcution to make sure any changes on the parameters are updated before the calculation (I believe that might be the case for when you are comparing the results on different PCs or different ZOS versions). Regarding the resampling please consider the case that you might be having the peak Irradiance selected within the settings:

By changing the sampling in this case it is expected to have different total power results.

Nevertheless, if you are still facing difficulties and considering the results are different. In order for me to check if this is an actual bug I will need POP's tool parameters as well as the optical system setup. The quickest way would be to open a case with us so you can share the files with me. If you do not have support though then will need to do the procedure through this post. Let me know if thats the case and will provide you with guidance.

Kind Regards,

Niki