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:

• https://support.zemax.com/hc/en-us/articles/1500005488601-Using-Physical-Optics-Propagation-POP-Part-1-Inspecting-the-beams
• https://support.zemax.com/hc/en-us/articles/1500005488621-Using-Physical-Optics-Propagation-POP-Part-2-Inspecting-the-beam-intensities
• https://support.zemax.com/hc/en-us/articles/1500005488621-Using-Physical-Optics-Propagation-POP-Part-2-Inspecting-the-beam-intensities?ka=KA-01603

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