I agree, but a common lens should behave in one dimension exactly as a cylindrical lens does. This is why I have a model for each dimension.
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OPT Lasers Cylindric lenses - NUBM44 beam correction tests
- Thread starter Milos
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I agree, but a common lens should behave in one dimension exactly as a cylindrical lens does. This is why I have a model for each dimension.
The app doesn't allow you to model for one dimension.
I've done a search to see if this type of lens in combination can be used to collimate a raw laser beam in the same way a typical beam expander does, I could find nothing to confirm that that is possible.
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The way the lens is designed on the China G-2s it is slightly more flush on the diode side, however it really depends on the barrel they're using. Some of the barrels have about 1mm of brass before bottoming out - what I would do on these when I was all about G-2s is grind the bottom so that it would be hella flush with the bottom of the lens, that way it would get close enough to actually focus..
What I've been doing a lot with my NUBM05T builds to shrink down that crazy NUBM-Line-of-Lines is I pull apart 3EGLs and use the larger of the 3 lenses, usually a doublet, and use only that and I crud you not, the beam profile seems to shrink over some of the full on 3EGL setups - also 1 lens vs 3 lens = more power output
Depending on how far I want the EFL I may have to try out a few different lenses, some of them are doublets while others are Plano-Convex or Plano-Maniscus.. but typically the doublets will require that you switch the barrel around so that it is THAT far away from the diode - but this distance will allow less of the original beam to contact the lens which nets less power, so I try to find one with an EFL that's close enough to the diode to capture the entire beam
What I've been doing a lot with my NUBM05T builds to shrink down that crazy NUBM-Line-of-Lines is I pull apart 3EGLs and use the larger of the 3 lenses, usually a doublet, and use only that and I crud you not, the beam profile seems to shrink over some of the full on 3EGL setups - also 1 lens vs 3 lens = more power output
Depending on how far I want the EFL I may have to try out a few different lenses, some of them are doublets while others are Plano-Convex or Plano-Maniscus.. but typically the doublets will require that you switch the barrel around so that it is THAT far away from the diode - but this distance will allow less of the original beam to contact the lens which nets less power, so I try to find one with an EFL that's close enough to the diode to capture the entire beam
I purchased today two cylindricals from Thor Labs. For the major axis, a focal length of 25.4mm and for the minor axis, a focal length of 150mm. This should give me a beam profile of 20x28mm and divergence of 0.039mRad x 0.093mRad, respectively. I decided to collimate the minor axis at a larger size to reduce divergence. Also, with only two lenses total and no clipping, the beam should have relatively high power. I had someone at Light Machinery check my numbers for my application and I was told it would work very well. I will post results when available.
Hi there. I noticed the spike in traffic from this thread to our beam propagation tool. This other lens design tool may be more useful for you.
https://lightmachinery.com/optical-design-center/lens-design-cloud/
Have fun -
Gregg @ LM
https://lightmachinery.com/optical-design-center/lens-design-cloud/
Have fun -
Gregg @ LM
Hi Gregg, I've got some questions about the Gaussian Beam Expander app.
Is this a correct result? https://lightmachinery.com/optical-...-beam-propagation/?key=IefemV-0IUKN9KD7m14kjw
Are there limits to what the app can calculate?
Are negative focal length lenses allow as would be used in a Galilean beam expander?
Thanks,
Steve
P.S. I may have more questions at a later time.
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Thank you.
Gregg, thank you for showing us the other app. It looks very useful. I look forward to trying it out.
Steve, I suspect the problem with your model is the 10 mRad divergence combined with 0.001 waist/emitter size. I doubt any real diode could recreate this model in the real world.
Lastly, I received my two cylindrical lenses from Thor Labs. They work exactly as planned, collimating the fast and slow axis exactly where I wanted them to. I get an extremely low divergence beam across the night sky. The catch: spherical aberration. Mainly with the short focal length, fast axis lens, I get too much splash from the aberration. The proper fix would be an acylindircal lens, but these skyrocket in cost, so I will reevaluate my approach.
P.S. I finally got my Sanwu G7. It has the best divergence and power out of all of the following that I have tried:
OPT 3 element
OPT single element
DTR 3 element
DTR G2 (won't screw far enough into my OPT diode mount to focus)
Sanwu G7
Steve, I suspect the problem with your model is the 10 mRad divergence combined with 0.001 waist/emitter size. I doubt any real diode could recreate this model in the real world.
Lastly, I received my two cylindrical lenses from Thor Labs. They work exactly as planned, collimating the fast and slow axis exactly where I wanted them to. I get an extremely low divergence beam across the night sky. The catch: spherical aberration. Mainly with the short focal length, fast axis lens, I get too much splash from the aberration. The proper fix would be an acylindircal lens, but these skyrocket in cost, so I will reevaluate my approach.
P.S. I finally got my Sanwu G7. It has the best divergence and power out of all of the following that I have tried:
OPT 3 element
OPT single element
DTR 3 element
DTR G2 (won't screw far enough into my OPT diode mount to focus)
Sanwu G7
Typically when I use the app I base the input numbers on a dpss green laser. I have an old green module without lenses and the beam based on a guess diverges at a rate of about 5-10 mrad. The emitting area is assumed to be very small.
Thanks for the replies. Three more questions if you don't mind. Three is a two part question.
1. Beam Waist Location (mm). I'm unable to visually interpret what a negative result indicates. What does it mean?
https://lightmachinery.com/optical-...-beam-propagation/?key=CFpLk4yUmEG9Yp7lBIqV5w
2. I've always read that the separation of two lenses in a Keplerian expander is the sum of their focal lengths, but the results indicate otherwise, why?
Example: https://lightmachinery.com/optical-...-beam-propagation/?key=8WEMsZ9K3UChjvcch4CWpw
3. Can this app accommodate different types of lenses? Does it matter? I've seen drawings of expanders using cemented lenses, but I've not read anywhere why that is done. I think this answers my question: "Note: this calculation is only valid for paraxial rays and where the thickness variation across the lens is negligable."
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Ok and thanks.
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Guys, sorry to post on an old thread, but I've read the entire thing and I'm still confused. Can someone help me figure out how to correct the output of the NUBM44 diode with a 3 element lens. I've been searching for the past hour, so I did try to find an answer. I need instructions 
, or links to some.
, or links to some.Guys, sorry to post on an old thread, but I've read the entire thing and I'm still confused. Can someone help me figure out how to correct the output of the NUBM44 diode with a 3 element lens. I've been searching for the past hour, so I did try to find an answer. I need instructions
Assuming by correction you want to circularize the beam you can't with a 3 element expander. However, if you mean 3 lenses with two being cylindrical and one being a positive focal length lens then you can. Which is it?
