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FrozenGate by Avery

Shaping the 445nm Beam

Exerd

Exerd

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I am very interested in shaping the output of the 445nm diode to something more useful. I would be willing to try different lens configurations to see what can be done about the problem.

Please let this thread document any ideas or projects for shaping the 445nm beam that arise.

List any ideas or lenses you may have in mind.

:beer:

My first idea is as follows. Use a small collar which has a stepped inner diameter which can fit a standard Aixiz spring inside it. Also inside the collar a cylindrical lens will be glued on its side. The collar will sit over the diode to shape the beam into a square. The spring will keep the collar and cylindrical lens seated close to the diode face. A standard lens will be placed after the shaping lens to achieve beam focus.

My first step in solving this problem is determining what size cylindrical lens will properly shape the beam at the given spacing distance.

Rough draft of a module with lens and collar installed right above the diode face, darkened blue areas show light passing lenses:
2nlbj7k.jpg
 
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That thread is showing standard lenses we all know about.

I'm talking about beam shaping.

I.E. Custom setups with cylindrical lenses before the focusing lens.

No one has yet changed the output shape of this diode.

I'd like this thread to stay short and to the point, please. ;)
 
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If you come up with a drawing, I will be happy to try and make a custom prototype piece for you to experiment with in trying to get the lenses mounted...

Just let me know! :)
 
Exerd said:
That thread is showing standard lenses we all know about.

I'm talking about beam shaping.

I.E. Custom setups with cylindrical lenses before the focusing lens.

No one has yet changed the output shape of this diode.

I'd like this thread to stay short and to the point, please. ;)
Click to expand...

LarryDFW and I have been doing some cylindrical lens testing.
I reported some of my findings in the thread linked above.
Dr. Lava has also tested with cylindricals (I have heard).

I'm still working on it. When/if I get better results I will share...
 
RA_pierce said:
LarryDFW and I have been doing some cylindrical lens testing.
I reported some of my findings in the thread linked above.
Dr. Lava has also tested with cylindricals (I have heard).

I'm still working on it. When/if I get better results I will share...
Click to expand...

I guess it helps if I read before making stupid assumptions. :yabbem:

I didn't realize anyone else had been testing these yet.

I am very interested in being a part of this experiment.
 
Members of photonlexicon have tested an anamorphic prism pair with great success. They managed to get the beam pretty much round, and with 0.8 mrad divergence! They are also organizing a group buy for the optics and parts right now.

Tested with anamorphic prism pair
 
Hmmm... still a 'bar' though...

Quote from his thread:

" It still is a little bit of a line because the slow axis is 0,2mrad.

at 30 meters I ended up with a 40x8mm beam"




Thats just a 'fatter' bar instead...

I measured at about 20 meters and got a line that is 2.2mm X 16mm...

That's using the AixiZ 405 glass lens.

I think 2.2mm X 16mm at 20 meters is much better that what he got at 30 meters. (unless he fine tuned it... I didn't read the whole thread after I saw those numbers in the first post)

Edit: Oops... I measured that at 20' not 20 meters... Sorry about that...

Hmmm... still makes me wonder what size it would be at 30 meters with AixiZ 405...

Just measured it at 30 meters with AixiZ 405 glass...

22mm X 63mm

So his prisms are pretty good!
 
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If putting before the main collimator lens, any short EFL cylinder lens will work, shorter the better, the idea is have the virtual focus point appear somewhere inside the die to cause the expansion of the fast axis to slow and equal the slow axis. To collimate you will need to make the focal spot of the lens appear at the diode facet. A longer fl lens will collimate the beam after the main collimator lens This is also the reason you need AR coated lenses too- the reflection from the fron face of a standard glass lens may kill it at higher powers.

I like to put the cylinder lens first to get a square beam, then correct with a main collimator lens, aperature and then expand with a 3x beam expander for serious work.
 
IMHO, the difficult is, mainly, about where to find small cylindrical (or better said, half-cylindrical) lenses at affordable prices for anyone (and no, idon't consider "affordable price" 98$ for a 3mm lens, LOL).

Once we got the lenses, we can speculate about how fit them (directly on the diode, or in holders, and so on), butt, i think, until we don't get these lenses, it's a bit hard to build something efficent ..... or i'm wrong ? ;)

Personally, i think that the better solution can be find a semi-cylinder, or oval-shaped cylinder (also if the semi-cylinder can be a better solution), with the exact focal lenght, or more close possible, for correct the fst axis near the slow one, when the lens is placed in contact with the diode, so it can be glued directly on the diode body, and interfer the less possible with the focusing element (the better solution can be add a FAC in front of the chip, i know, but first, you need to find an 450nm AR coated FAC, and second, this require diode decanning, with all the related problems)
 
Something else to consider, is that cylindrical lenses, and anamorphic prisms can be used to SLOW the FAST AXIS, or can be used to EXPAND the SLOW AXIS.

By Slowing the Fast Axis, you get a beam that is more square, and that will leave the aperture at a smaller diameter. This is good for burning at close range.

By Expanding the Slow Axis, you get a beam that is more square, but is LARGER in diameter. THIS results in a MUCH better divergence. As in, .7-1.6 should be easily achieved!

So it all depends on the application of that diode. For beam shows, I recommend Expanding the Slow Axis. For Close Range pointing and burning like we do with greenies, we ought to Slow the Fast Axis. Both beams should still be focusable.

I would not try to de-can this diode. It's facet it particularly larger than those of the single mode 12X BRs we all know and love. The larger facets are more susceptible to damage from airborne particles because of their larger surface area.
 
Is possible to use a couple of prisms, as you say, but i don't suggest this ..... first, they require a lot of space, and second, from refractions and losses, you probably end with 30 to 40% of power loss in the process .....

Also, yes, if you need to focus in distance, correcting the slow axis with a negative lens is better, but then you need a larger lens for focusing better the beam, and a more long lens holder ..... anyway, with this diode used at the maximum powers, or near them, i suppose that the needed host is so big that this is not a problem, at the end ..... :)
 
I wish this prism assembly was AR coated for a lower nanometer range: Thorlabs.com - Anamorphic Prism Pairs

It sure looks like a size of package that could be dealt with in a handheld.

Unfortunately, the price is not something many of us would be willing to deal with, either.
 
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I found very prisms in a photo where they are being used! This gives me some good ideas... and *Ahem (Jayrob) might want to take a look. The machining required would not be complex. This DOES tell me that Anamorphics are out of the question when it comes to portable builds.

Here they are shaping a couple of diode arrays..
ldbc1.jpg


Pic From Repairfaq
 
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