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lost of beam intensity in a non-sequential optical system


Maryam

I have a non-sequential optical system consists of several lenses and mirrors. The incoming laser beam passes through them and then I use a rectangular detector to collect info about the outcoming beam. I am interested in knowing whether I lose any intensity if the divergence of the incoming beam increases. Is there a way in Zemax to find out the lost intensity? 

 

Thanks in advance and best regards,

Maryam

Best answer by Ray

Hello Maryam,

You should expect power losses from at least Fresnel losses and absorption at the mirrors.

Then, as you change the beam divergence with the optics, I would also expect the intensity (as in “radiant or luminous intensity”, not the power) to change (it can even increase if your outgoing beam is more collimated than the starting one).

You can set incoming and outgoing detectors to monitor the radiant intensity and compare the values (peak or average if you use 1 pixel).

Best regards

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  • Ultraviolet
  • 99 replies
  • Answer
  • February 5, 2025

Hello Maryam,

You should expect power losses from at least Fresnel losses and absorption at the mirrors.

Then, as you change the beam divergence with the optics, I would also expect the intensity (as in “radiant or luminous intensity”, not the power) to change (it can even increase if your outgoing beam is more collimated than the starting one).

You can set incoming and outgoing detectors to monitor the radiant intensity and compare the values (peak or average if you use 1 pixel).

Best regards


Maryam
  • Author
  • Infrared
  • 13 replies
  • February 10, 2025

Hi Ray,

Thank you very much for the response. Instead of increasing the divergence first I changed the size of my detector ( made it much smaller) and then performed the ray tracing. I don’t see energy lost when I perform ray tracing. However, when I look at my detector ( for example inverse false color for radiant intensity) I see that the surface of the doctor is full so some rays might be lost but how can I see that?

 

Thanks in advance and best regards,

Maryam 

 

 


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  • Ultraviolet
  • 99 replies
  • February 11, 2025

Hi Maryam,

Do you use enough pixels on your detector ? (a 1x1 pixel detector always looks full).
One way to see if you have light missing a detector is to add another bigger detector just behind it (say 1um). If the first detector is made absorbing, you should event see its shadow. Note that you should not put the two detectors at the same position, or you may have some unexpected results.

Best regards


Maryam
  • Author
  • Infrared
  • 13 replies
  • February 11, 2025

Hi Ray,

 

Thanks for the reply. I use 10*10 pixels for 1e+6 rays. Indeed I am using a bigger detector behind to see whether there is any rays hitting it. But what I am wondering is that how about changing the size of my own detector? Unfortunately, I don’t know the exact size of the detector in my real system at this moment. I don’t actually have a real detector but have an aperture of about 25*25 mm^2. But I can make the detector size bigger and bigger to avoid intensity lost which doesn’t make sense. Is there any other way to find out if I’m loosing any intensity except that relying on the detector size? and how can I find out the limit on the max and min angle of my detector by knowing it’s dimension ( if it’s 25*25 mm^2 for example)?

 

Thanks a lot and best regards,

Maryam


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