Hi Kaia,

Glad you are finding the tools useful.  When using us_gskew.dll, the “correct” value of Object Space NA depends on what you are doing, but could be one that produces the same divergence as the Gaussian beam you are modeling, for example a value of (wavelength)/(pi)/(waist radius) would produce rays with a maximum divergence equal to the 1/e^2 beam divergence. But you may want to analyze with rays further out than the 1/e^2 point to ensure that the optics have low aberration out to the edge of the beam.  What I might typically do is set the Object Space NA to 1.3*(1/e^2 divergence) and use Gaussian apodization with an apodization factor of 1.69, then the launched rays are fairly representative of where the optical power is through the system.  Remember that what the aperture setting does is define which rays are used to optimize and analyze your system.

In the example file, I used a high NA so that the beam width was exaggerated on the layout diagram, so that the Gaussian beam shape was clearly visible.  The high NA has no real design or analysis purpose in that file. 

Paul C.

Hi everyone,

This thread is now closed. Thank you so much for submitting your questions. And a special thank you to @PaulC for a great webinar and discussion!

If you’re interested in learning more about how OpticStudio handles laser beam propagation in general, check out our tutorials on the topic:

• Laser & Fiber Learning Plan – Zemax
• Modeling Laser Beam Propagation in OpticStudio – Zemax

If you have any other questions about this topic, feel free to submit them to our general discussion forum here: Got a question? | Zemax Community.