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Question about highdivergent diodes like the NUBM44

Accutronitis

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I know the standard way to tame the fast axis on a 44 which consists of cyl lens pair correction which is just like a beam expander for one axis as the beam exits the collimator it is still very narrow and passes through the first cyl lens which spreads out the beam to a wider diverging beam which hit the output cyl lens which converges the beam to a focusable focal point, But the beam exits the laser much wider than the slow axis so the beam on exit looks like a small stubby rectangle when both axis's are focused to infinity.

With out a beam expander no collimator can bring such a widely diverging axis to a focal point and there for when you focus the slow axis to a point the beam end up being a thin line which exits the laser on both axis's close to the same size but the fast axis fans out no mater how you focus the collimator.

Why couldn't a different approach work like for example the same diode and collimator that has a slowly diverging fast axis on exit BUT this time use a lightly converging cyl lens as the input converging the beam to a point but right before it can get to that point put a diverging lens there that will lightly diverge the converging beam to a parallel collimated axis that is the same small size as the slow axis as they both exit the laser with both of the axis's slowly converging to infinity at close to the same rate ???

Pardon the crude drawing that I knocked out very fast to try and get my idea across, But is there any reason why this approach couldn't work ??? Disregard where it says "beam expander" and substitute "cyl lens pair" in it's place.....

 
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steve001

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I know the standard way to tame the fast axis on a 44 which consists of cyl lens pair correction which is just like a beam expander for one axis as the beam exits the collimator it is still very narrow and passes through the first cyl lens which spreads out the beam to a wider diverging beam which hit the output cyl lens which converges the beam to a focusable focal point, But the beam exits the laser much wider than the slow axis so the beam on exit looks like a small stubby rectangle when both axis's are focused to infinity.

With out a beam expander no collimator can bring such a widely diverging axis to a focal point and there for when you focus the slow axis to a point the beam end up being a thin line which exits the laser on both axis's close to the same size but the fast axis fans out no mater how you focus the collimator.

Why couldn't a different approach work like for example the same diode and collimator that has a slowly diverging fast axis on exit BUT this time use a lightly converging cyl lens as the input converging the beam to a point but right before it can get to that point put a diverging lens there that will lightly diverge the converging beam to a parallel collimated axis that is the same small size as the slow axis as they both exit the laser with both of the axis's slowly converging to infinity at close to the same rate ???

Pardon the crude drawing that I knocked out very fast to try and get my idea across, But is there any reason why this approach couldn't work ??? Disregard where it says "beam expander" and substitute "cyl lens pair" in it's place.....

First thing. Run on sentences are difficult to read, use punctuation where needed. Second thing. Spell check. I'm no genius when it comes to sentence construction, but writing well makes it easier to comprehend. The drawings helped.

What is the thing labeled "collimator"?
 

Accutronitis

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First thing. Run on sentences are difficult to read, use punctuation where needed. Second thing. Spell check. I'm no genius when it comes to sentence construction, but writing well makes it easier to comprehend. The drawings helped.

What is the thing labeled "collimator"?
A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device).

If you don't know that then your not the person I'm looking for to answer my questions but thanks for the criticism, Oh and all the spelling was correct but thanks anyways... :rolleyes:
 
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steve001

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A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device).

If you don't know that then your not the person I'm looking for to answer my questions but thanks for the criticism, Oh and all the spelling was correct but thanks anyways... :rolleyes:
A collimator appears to be a good idea at first glance. A collimator consists typically of a single positive lens in a tube or the same coupled with a fiber optic. Typically used to calibrate. In either example you'd have to consider over filling thereby losing light. In short it complicates the setup too.
The other examples won't work, but I don't have time to explain why.
 

diachi

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If you're reducing the beam diameter then the divergence must increase, that or you must lose significant amounts of power. No free ride when it comes to laser beam correction. The fast axis starts off as the smaller axis but has the higher divergence, to improve that divergence you need to make the fast axis larger at aperture.
 

Accutronitis

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A collimator appears to be a good idea at first glance. A collimator consists typically of a single positive lens in a tube or the same coupled with a fiber optic. Typically used to calibrate. In either example you'd have to consider over filling thereby losing light. In short it complicates the setup too.
The other examples won't work, but I don't have time to explain why.
If you're reducing the beam diameter then the divergence must increase, that or you must lose significant amounts of power. No free ride when it comes to laser beam correction. The fast axis starts off as the smaller axis but has the higher divergence, to improve that divergence you need to make the fast axis larger at aperture.
Thanks, Just out of curiosity how much time did it take you to explain this diachi ?

diachi you state "If you're reducing the beam diameter then the divergence must increase" But as the fast axis leaves the collimator it is diverging (increasing) or do you mean that divergence must increase further like it does with a beam expander ?

What would it take to make the fast axis leave the laser narrow and with little divergence just like the slow axis does ? The slow axis leaves the laser very narrow and it stays that way as far as the eye can see (I know it is actually slowly diverging) with cyl lens correction it acts like a beam expander for the fast axis so it made that axis leave the laser wider than the slow axis, is there any way around that ? Without going to a different diode of course.....

Couldn't the cyl lens pair (that expands the fast axis before converging it) be adjust so the cyl lens pair converges the beam to a short focal point and add a concave cyl lens before the focal point to straighten the beam back to a parallel column of light on that one axis ?
 
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RedCowboy

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This is what I meant by getting your concave cylindrical as close to your G2 as possible, that way you expand the axis from the smallest possible point.
 

Accutronitis

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This is what I meant by getting your concave cylindrical as close to your G2 as possible, that way you expand the axis from the smallest possible point.
For me to get it any closer I would have to cut part of the G2 off or can I flip the first lens around and put the flat side to the G2 ?.....
 
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diachi

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Thanks, Just out of curiosity how much time did it take you to explain this diachi ?

About 30 seconds. I type fast. :D

diachi you state "If you're reducing the beam diameter then the divergence must increase" But as the fast axis leaves the collimator it is diverging (increasing) or do you mean that divergence must increase further like it does with a beam expander ?

The divergence must get worse, i.e. the numerical value for the divergence must increase. A beam expander decreases it while increasing beam diameter.

What would it take to make the fast axis leave the laser narrow and with little divergence just like the slow axis does ? The slow axis leaves the laser very narrow and it stays that way as far as the eye can see (I know it is actually slowly diverging) with cyl lens correction it acts like a beam expander for the fast axis so it made that axis leave the laser wider than the slow axis, is there any way around that ? Without going to a different diode of course.....

You'd need to get the collimating lens closer to the die to see any improvement there, or have a FAC (fast axis correction) lens on the diode. That can still only offer a limited improvement. That or sacrifice power for better beam specs.

Couldn't the cyl lens pair (that expands the fast axis before converging it) be adjust so the cyl lens pair converges the beam to a short focal point and add a concave cyl lens before the focal point to straighten the beam back to a parallel column of light on that one axis ?

Nope, that wouldn't work. If you're reducing the beam diameter on one axis (which is collimated) the divergence on that axis must increase. There's no way around it, other than sacrificing lots of power. That doesn't mean this will work if the beam/axis isn't collimated, you'll encounter the same issues.
See answers in red. Divergence is inversely proportional to beam diameter and proportional to wavelength.

Unfortunately that's how life is with these diodes (and in fact, all lasers), they can only be improved so much and you must always make a trade-off somewhere else for those improvements.
 
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RedCowboy

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NO, I wouldn't do that, I just meant don't put it inches away.

Ideally we would use a FAC lens right at the emitter, but I won't remove the can and the cost and difficulty in placing the tiny fused silica lenses focus, well it's a moot point really.

What is your beam width at 10 meters, not if you adjust it there, but at your dead set/infinity focus of your cyl lenses?
 

Accutronitis

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NO, I wouldn't do that, I just meant don't put it inches away.

Ideally we would use a FAC lens right at the emitter, but I won't remove the can and the cost and difficulty in placing the tiny fused silica lenses focus, well it's a moot point really.

What is your beam width at 10 meters, not if you adjust it there, but at your dead set/infinity focus of your cyl lenses?
I'm resetting all of the lenses one lens at a time, Dang to get the beam dead center means moving the lens ever so small from side to side !!!

Thank you very much diachi for taking the time to explain that, Now I understand what's going on much better and it's a very good day because I learned something new !!! I want to rep you guys but I have to spread it around some more before I can dang it !

Edit - that reminds me diachi which side of the first lens of the cyl pair faces the G2 ? the flat side, Or the concave side, Or does it really matter ?

The reason I ask is because I noticed with my JL BE 10X the first lens is a Plano-Concave lens just like the first lens in a cyl pair only it's Spherical Lens instead of a cyl But it has that lens with it's flat side facing the G2 ???
 
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diachi

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diachi can you please take me off your PM blocked list ?

Try now. FYI, you were not explicitly blocked, just not whitelisted. Anyone not in my "contacts" is not able to PM, so that goes for many people here. :beer:
 

steve001

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I'm resetting all of the lenses one lens at a time, Dang to get the beam dead center means moving the lens ever so small from side to side !!!

Thank you very much diachi for taking the time to explain that, Now I understand what's going on much better and it's a very good day because I learned something new !!! I want to rep you guys but I have to spread it around some more before I can dang it !

Edit - that reminds me diachi which side of the first lens of the cyl pair faces the G2 ? the flat side, Or the concave side, Or does it really matter ?

The reason I ask is because I noticed with my JL BE 10X the first lens is a Plano-Concave lens just like the first lens in a cyl pair only it's Spherical Lens instead of a cyl But it has that lens with it's flat side facing the G2 ???
You've asked some interesting questions. If I were you I'd look for a used opitical board with lens holders and experiment. Something such as what this engineer is using in this demonstration. https://youtu.be/ac-vVNbQt2I
 

diachi

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You've asked some interesting questions. If I were you I'd look for a used opitical board with lens holders and experiment. Something such as what this engineer is using in this demonstration. https://youtu.be/ac-vVNbQt2I

Small breadboards come up on eBay fairly cheap from time to time, the big ones are pricey, even used. You can get used posts/mounts to match on eBay too, sometimes there'll be a whole bunch for sale in one lot.
 
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