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488nm GH04850B2G

crazyhobo

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I've picked up a 488nm GH04850B2G build which is great, but I think it has the G2 lens, and definitely has the large rectangle artifact on one side of the spot.

Would swapping the lens for the G8 totally remove that artifact?

Also is 275ma still the agreed upon safe current?
 
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RedCowboy

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Factory spec is around 125ma which gives you 60mw
I drive mine @ around 250ma which gives you 120mw
Some people push to 375ma which gives you 160mw

So you can see the efficiency hasn't dropped at twice the factory current rating but at triple is has started to drop so 275ma should be just fine although anything above the factory spec will likely result is a lower MTTF but probably not enough to matter to us and the beam looks much better @ 120-170 than at 55-60mw

The G8 will reduce the size of the box artifact but it's difficult to get rid of altogether, as it's a reflection I suppose you could de-can the diode but MTTF could be drastically reduced.....however @ 275ma maybe not so much that it wouldn't be worthwhile......I would use a little Teflon tape on the lens barrel threads and set the focus to infinity and leave it alone if running de-canned.....I may have to try that and see how well it holds up.
 

farbe2

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Decanning will not help with the artifact. The "box reflection" is actually caused by the laser die/crystal itself.
The lens just images the whole die, including the non emitting portions. The non emitting portions cause the "reflection".
I will make a thread on this later.
 

RedCowboy

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I knew it was a reflection but I thought the can's window was a factor........so in that case a mask ( a thin disc in front of the can or attached to the can with a beam size pinhole ) could block the artifact. Maybe have the holes cut with a wire EDM so the hole has a nice square edge once the diameter has been determined.

I can see how the facet is making a reflection as the emitting region at the p/n junction is but a tiny slit at the top of the substrate stack which is covered with the front facet/reflector but isn't the can window reflecting diffuse light back at the facet which is making it reflect outward ?

800px-Laser_diode_with_the_case_and_window_removed-powered_off.jpg



1024px-Simple_laser_diode.svg.png
 
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farbe2

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I will post a thread now, I will use your picture if it is ok?
 

farbe2

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Have a look here:
 

crazyhobo

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Thanks for the help guys! And for the detailed explanation in the above thread Farbe - also nice work on the paint mod!

I just got this build so I don't want to de-can the diode, but as for the G8 reducing the box reflection's size over the G2, how much smaller are we talking? Half?

Knowing what the reflection is now strangely makes me not mind it as much.

Still, if the G8 makes the box considerably smaller I'll give one a try.

Unrelated, but I did turn up the power a bit tonight, and it's now at ~140mw, up from ~90mw. The color shifted ever so slightly as expected to that even more stunning color. Very cool. EDIT - pic below!

EDIT - I see on page 6 of the G8 lens thread that the artifact is still there when used with this diode, so I'll stick with the higher power G2.

Hurst.jpg
 
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