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Pushing the NDB7675 to higher spectrum

olympus mons

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I read in another thread people discussing pushing the 1.4W 462nm Laser Diode(NDB7675) close to and even past 2.4A to get it to jump spectrum to 473nm. That this action was unique this diode and the M462 doesn't act the same when pushed hard.
Does anyone have any experience doing this or wish to add their 2 cents?

Is the color of 472+ more visible than 462nm? Is it a nicer blue?
Thanks,
Jeff
 



Pi R Squared

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Of course it is more visible and brighter, it is moved closer to the brightest part of the spectrum. I wonder though how safe it is to do this. The data sheet says absolute maximum of 1.7A, we all know this is generally a conservative figure but I would be worried the diode may degrade over time or not last long, I don't think enough people have overdriven these that much for long enough to tell yet how well they will hold up.

Alan
 

olympus mons

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Of course it is more visible and brighter, it is moved closer to the brightest part of the spectrum. I wonder though how safe it is to do this. The data sheet says absolute maximum of 1.7A, we all know this is generally a conservative figure but I would be worried the diode may degrade over time or not last long, I don't think enough people have overdriven these that much for long enough to tell yet how well they will hold up.

Alan
Hmmm okay good to know thanks. I may be okay with shortening the diodes life for a brighter beam. They're not terrible expensive to replace if it dies. I just got a 445nm and I'm not too happy with the color and visibility even at 2W+. 472 sounds pretty nice.
 

DTR

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Yea there is a noticeable difference between 472nm and 462nm just as there is between 462nm and 445nm. 472nm will be a bit brighter per mW and is a little closer to sky blue or aqua in color. I would say 445nm is blue with a hint of violet, 462nm is more of a true blue, 472nm would be between blue and sky blue and 480nm would be full sky blue.

The downside driving them like this is you are frying the NDB7675 running it so high. This is actually past the point of foldback meaning you actually get less power output than if you turn the current down. You basically have heat being generated faster than it can be removed causing a sharp temperature rise in the diode which in turn causes the wavelength to shift upwards. This will undoubtedly cause a significantly shortened lifespan for the diode.:beer:
 
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olympus mons

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Yea there is a noticeable difference between 472nm and 462nm just as there is between 462nm and 445nm. 472nm will be a bit brighter per mW and is a little closer to sky blue or aqua in color. I would say 445nm is blue with a hint of violet, 462nm is more of a true blue, 472nm would be between blue and sky blue and 480nm would be full sky blue.

The downside driving them like this is you are frying the NDB7675 running it so high. This is actually past the point of foldback meaning you actually get less power output than if you turn the current down. You basically have heat being generated faster than it can be removed causing a sharp temperature rise in the diode which in turn causes the wavelength to shift upwards. This will undoubtedly cause a significantly shortened lifespan for the diode.:beer:
Thanks DTR, that makes it easy to understand . So are there any 472 diodes on the market for handheld lasers? After your explanation and knowing what host this would be going in I don't think its a good idea.
BTW I just ordered my 1.4W 520nm from you. Im going to build that one first but the 462 may be next. Thanks for your help.
 

Down with Umbrella

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Here's the catch, I can only speak from what I've seen on the forum but don't think an over driven NDB7675 guarantees you achieve 470s. Correct me if I am wrong but the absolute max they can be pushed is 3.0 A. It depends on the diode batch. RHD has done some testing with these diodes to the death.
 

Alaskan

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What if you push the current and cool with a TEC, would it then jump to the 470's as well as safe the diode from deterioration and failure?
 

Pman

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Personally I would be too edgy about pushing one that hard as they aren't exactly cheap.
Just looked up a couple of places that sell the 472/3 and they are quite pricey so I can see the temptation to push the 462nm.
Wondering what DTR/Jordan thinks will be the most likely nm for 2015 to be offered.
Sure would be nice to see something more affordable pop up that's some odd color we wouldn't expect but I guess that's VERY unlikely:(
 
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bdgreenb

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What if you push the current and cool with a TEC, would it then jump to the 470's as well as safe the diode from deterioration and failure?
The wavelength shift and Theoretical degradation are causes from the same effect. If you cooled it, you wouldn't get the wavelength shift, but also may protect it from heat damage. Perhaps you would end up getting a higher power for the current, but not the wavelength shift.

Hmmm i might put mine in the freezer and test it to see if i get a higher output.
 

Atomicrox

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I don't think putting it in the freezer is a good idea. Did that to a cheap 635nm pen and it developed a lot of dot "artifacts" afterwards. Probably due to condensation or something. You can cool a laser to increase the current and/or lower WL, but you need a proper setup.
 




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