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Terrible beam off of Oclaro 638nm 700mW diode with new G2 lens

XenondiFluoride

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Hello again,
I recently got a new G2 lens to replace the one in my oclaro diode setup. (it got dropped and stepped on....) the odd thing is, now the beam is at best a square, no dot option at all. If you really try to get it tight, it pulls out into a line that is perpendicular to that of the normal light from the laser die. Now it can hardly light a match, and I know that to be complete bunk. The odd thing is, if I put the same lens on the M140, it works just a normal.

Any ideas as to what i am missing?

I know the oclaro has a not so great spot size, but this is terrible. I'll try to get a picture of it up soon. for now I'll say that at 20 feet, the tightest i can get is a 8 inch square like shape.

And it is just as bright as ever, with the lens off there are no artifacts to see.
 
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paul1598419

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Yeah, these have awful beam specs. You always trade off divergence for power when you use a G2 lens. It is properly focused when you see a tight line.
 

XenondiFluoride

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I must clarify, this tight line is not like that of the dye shape getting "pushed into a circle" as you bring the lens into focus, but a very thin line that as I mentioned was not in the original plane of the dye emission. I have never seen a 90 degree flip like that. (or more like it squashed it vertical?)
 

paul1598419

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Yes, the Oclaro and the Mitsubishi 635nm diodes both have this type of beam. It is not as bad with a multi-element lens, but with a G it is awful. As you tend to unfocus the beam it will look more like a large rectangle or square. It's the nature of these diodes.
 

XenondiFluoride

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Bummer, so what should I do?... because the beam really is not even that powerful (in terms of burning and focus) in its current state. A multi element takes a pretty hefty performance hit though.

Thank you for the support so far though.
 

paul1598419

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You can still burn with it. You just have to get really close. If you want better beam specs you need to go with a single mode diode and it will have far less power.
 

XenondiFluoride

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Yeah, I figured when I ordered a while ago it that multimode would be tolerable. clearly for this one it is not. well if nothing else it looks neat...

Thank you for all the help!
 
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DTR

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Yea the most common buying of those is for use in projectors and they use correction optics like these after a G-2 which you would have to work to make a portable with them and it would be huge.
Cylindrical lenses - Opt Lasers

I wonder if anyone has tried using a beam expander like some have done with the high divergence high power NUB diodes?
 

paul1598419

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I've never heard of anyone buying cylindrical lens pairs for one of these diodes as the lenses cost twice as much as the diode does. Can't say about the BE.
 

dden4012

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Your burning with the wrong color. Imo stick to single mode reds they have a great beam. The x16 bluray is the burner I would suggest. The oc638 has a horrible beam and the 3 element barely helps.
 

Lifetime17

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Hi X,
I just went down to my shop and put on a 3X BE on a Mitsu500 and it does improve the beam bit. It eliminates the lines on the ends and make the square almost oval on the ends..

Rich:)
 

paul1598419

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Hi X,
I just went down to my shop and put on a 3X BE on a Mitsu500 and it does improve the beam bit. It eliminates the lines on the ends and make the square almost oval on the ends..

Rich:)
I wonder how much of that is clipping of the beam's sides and how much power is relinquished in using the BE.
 

Accutronitis

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I wonder how much of that is clipping of the beam's sides and how much power is relinquished in using the BE.
If you focus the beam with something like a G2 lens before the beam enters the beam expander there should not be any clipping from the BE ?
 
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XenondiFluoride

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Hmm, well thank you for all the replies. I used to have a 16X or 24X red one that worked great until it got popped by a careless current knob turn. I'll have a chance to get another one like it hopefully at the upcoming earth day recycling fair in my area.

what stinks is that it is very well pressed into the copper module, so looks like I'll have to keep it in there and buy more modules...

Next time I'll make sure I will not run into this by asking you all and /or keeping this diode in mind. Any fun single mode diodes you all would recommend that are fairly cheap? I want more!
 

dden4012

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Search bar at the bottom of the site.
Single mode red 635
Single mode blue 450
Single mode green 520
 

DTR

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I've never heard of anyone buying cylindrical lens pairs for one of these diodes as the lenses cost twice as much as the diode does. Can't say about the BE.
Yea it is the most cost effective way to get red in light show projectors per mW. It is a bargain compared to using many single mode diodes and all the optics required to combine them. Check this out for a good read. A lot of work went into designing this correction setup.

https://www.photonlexicon.com/forums/showthread.php/15785-Mitsubishi-ML520G71-Red-Holy-Grail-or-Flashlight-Fail

I can see how from a pointer point of view it would seem expensive.
Check out these searches for a lot more info.

https://www.google.com/search?q=638nm+correction+site:www.photonlexicon.com

https://www.google.com/search?q=638nm+correction+site:laserpointerforums.com
 




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