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NSC Herriott Cell (Multipass, resonant cell) Simulation

Hello,
I’m trying to simulate a stable Herriott Cell and am having some difficulties.

Requirements of Cell:
Mirror spacing: 375mm
Concave mirror radius: 750mm
Other mirror is flat
Both mirror diameters: 50mm
Quad flat mirror: has a quadrant that is a 50/50 mirror that lets the incoming and outgoing beam come in and out of the cell. Ideally, incoming and outgoing beams should produce an interference pattern.

Figure above shows how the beams reflect between the mirrors. 

The image below is the current simulation I have running. There is a hole in the center of the first mirror, so that the beam can enter and exit. However, in the experimental setup, there is a mirror with a quadrant that acts as a 50/50 mirror so the beam can enter and exit in this quadrant after bouncing around 4 times inside the cell. I added the hole in Zemax because if I let the beam keep bouncing, I would get the ‘not enough intersections’ error which is due to the cell being stable and will keep bouncing back and forth infinitely. I wanted to know if there are any suggestions/recommendations on how to proceed with a quad mirror model (ie. Is there a way to limit how many times the light bounces back and forth instead of letting it go to infinity?) 

If we didn’t have the max intersections rule, OS would simply appear to hang as the rays would be traced forever. So, set ‘Use Polarization’ and use some coatings on the mirrors. This will give a reflection  loss per pass that will eventually bring the intensity of the beam below the threshold at which OS stops tracing. 

Hi Mark,

Thanks for your response! I did initially try the method that you suggested but as you said it would rapidly decrease the intensity of the beam. For my project, I am trying to compare the beam profiles coming into and out of the cell (they should be exactly the same) so a lower intensity beam would not be useful in this application.

Do you have any other suggestions on how to go about this issue?

 

Well, they should be the same materials and coatings as you use in real life, so the output should be what you would get at the exit of the real Herriott Cell. 

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