Hello,

Thank you for sharing a sketch of your system.

To analyze the beam profile at the 1st image plane, you could either use sequential or non-sequential. POP is recommended in in these cases: 

• When investigating the diffraction of a system that has an aperture at an intermediate focus (pinhole spatial filter)
• When analyzing diffraction effects close to a hard aperture (ringing of Gibbs phenomenon)
• When propagating a far distance (z >> r) in free space where a beam will “self-diffract”

So apart from these cases, I would not recommended using POP as it is not a straight forward tool. For more information, have a look at our tutorial: https://www.zemax.com/blogs/free-tutorials/modeling-laser-beam-propagation-in-opticstudio

For the 2nd image plane where you want to see interference fringes, I would recommend non-sequential.
These samples files \Zemax\Samples\Non-sequential\Coherence Interference and Diffraction will help you too.

So I think non-sequential would be a good option in your case.

Sandrine

If you're looking for interference fringes between the two beams, use non-sequential mode as it handles shearing interferometry (where the two beams partially overlap) very easily. See the sample file Samples\Non-sequential\Coherence Interference and Diffraction\Interference Example 1- A Simple Interferometer.ZMX and the other examples in that folder.

- Mark

Thank you Ms. Sandrine and Mr.Mark for the reply and suggestions. 

So here is my system that I had done today, beside using the Non- Sequential mode in my system, I create a system that fully used Sequential mode in my system. In my system, the main point is to used POP to analyze the beam profile in first image. For that reason, I chose Sequential mode to create the system. I need someone help to check for my system either it is ok or not?

Hello

The best advice I can give you for POP is to have a look at those 3 articles. It explains step by step how to check your beam through the POP propagation:

• 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/1500005488641-Using-Physical-Optics-Propagation-POP-Part-3-Inspecting-the-beam-phases 

I just noticed when I open your file that you have set the Surface to Beam parameter in POP to 5.3e-05.

This distance is the distance from the Start surface to the beam definition. So if the beam waist is at the object, it should be -7.814000000000000E+000.

Let us know how it goes and do not hesitate if you have any follow up questions.

Sandrine