Dear all,
I am Trying to generate and propagate a Donut beam using axicons. My problem is thaht when I use the POP tool the beam “disappears” after the first axicon surface, Namely before the axicon I see the gauss which propagates, after the axicon I see only a blue field with a red pixel in the middle. Noone as Idea what is gong wrong and haow to fix the problem to see the beam evolving during its propagation?
I attach the file to give you the possibility to have a look.
Best regards
Gabriele
Hi Gabriele,
In the sample files that come with the installation of OpticStudio, there is one file with an axicon. It can be found under "\Zemax\Samples\Physical Optics\Axicon with ring focus.ZMX".
If you open that file, you can check the POP settings. In the odd asphere properties, in the POP section, the output pilot radius has been set to Plane:
This is because by default the software doesn’t find the good pilot radius.
So I would recommend checking your phase at each surface. Have a look at those articles to learn how to do it:
If the sampling is not correct, then try the Plane option. Or another way to do it is to fit the odd asphere (axicon) with a sphere and then replace temporarily the axicon with the sphere to get an idea of the pilot radius needed in that simple case.
Let us know if that helps.
Sandrine
Hello Sandrine,
Thanks a lot for your help. I tried to change the Physical optics propagation settings as in the example. I come a bit further and I succeeded to get rid of the Warnings in the Report . Nevertheless the results are heavily undersampled and heavily affected from Aliasing.
Gabriele
Hi Gabriele,
Just posting a summary of the discussion we had on support. The axicons in your system have an angle of about 17 degrees and introduce a lot of phase to the beam and the software is struggling with the sampling. I used the merit function from the article https://support.zemax.com/hc/en-us/articles/1500005488641-Using-Physical-Optics-Propagation-POP-Part-3-Inspecting-the-beam-phases to calculate the required sampling and I got 63000.
POP can have a very high sampling like this only using ZOS-API.
But another tool to run your analysis can be the Huygens PSF. It gives a "ring".
Sandrine
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