Learning Forum

[Anonymous 1996]

I am trying to visualize Fresnel's diffraction pattern of a laser source passing through a solid slit of 5 μm. I want to model the diffraction observed in the real world when a laser passes through these slits. How can I achieve this in Zemax? Any help and tutorials would be much appreciated. Current Approach:

1. Non-sequential simulation.
2. Coherent laser source.
3. CAD model of a 5 μm slit with absorption properties.
4. Ray trace with split and scatter NSC rays.
5. Visualize the coherence irradiance in the detector

My current setup.
Original image what I want to model and see:

Thank you in advance for your assistance!

[Ethan Keeler]

Hello. Thanks for your question!

Modeling diffraction can be quite tricky, and unfortunately, a ray-based analysis cannot correctly capture the behavior of diffraction through a 5-μm slit (or any diffraction for that matter). Rays are a geometric simulation; you need to consider instead a wave-based simulation that can model diffraction from the edges of your slit aperture.

My suggestion would be to instead consider the Physical Optics Propagation tool in OpticStudio's Sequential mode. You would need to know the LED emission profile to create the correct initial representation of the beam. Modeling this beam correctly could be challenging, but you could start with just a simple Gaussian beam definition to understand how to use the tool. Then you could try propagating that beam through a narrow slit aperture (applied as a rectangular aperture, an example shown below):

I do want to caution you, though; POP can be a very complex tool. You need to be very careful about how you set the simulation up, and due to its complexity, I would first suggest that you study this series of Knowledgebase articles to better understand the pitfalls and its usage: Exploring Physical Optics Propagation (POP) in OpticStudio – Knowledgebase (zemax.com) and Using Physical Optics Propagation (POP), Part 1: Inspecting the beams – Knowledgebase (zemax.com).

[Anonymous 1996]

Dear Ethan,

Thank you for the suggestions. From my understanding, it is not feasible to simulate this functionality in non-sequential mode. However, modeling every aspect of my non-sequential system in sequential mode to study these effects is a stretch.

I will refer to the links you provided and will let you know if any questions arise.

Regards,
Navaneeth