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First Laser Diode acting like LED

JohnScolaro

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Hey guys, this is my first post, but I've been following this site for a long long time. I have finally ordered in all my parts to make a LM317 laser driver for my 300mw 808nm laser diode. And I connected everything up after testing, and all went well. The laser diode came on at an output of around 100mw, and continued to get brighter until I couldn't actually make it any higher at around 800mw input. (Which is ridiculously strong. But fantastic, because I'm looking for some solid burning action.)

The only problem is the laser diode seems to be emitting incoherent light, in all directions like an LED rather than in a coherent beam like a laser diode. I was wondering if most lasers do this, and mine just needs a casing, or whether there is something wrong with my laser diode.

How do I focus it? So it is in a beam, so I can get down to the burning part.

Please don't even mention safety, because i'm not new to electronics and lasers in general, just new to making them, and please dont ask why I want a burning laser, because obviously I want to burn things.

Thanks! :D
 

Things

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Yes, you need a lens on the output. The most common people here use are "AixiZ" modules.

If you were running the diode bare without any sort of heatsinking, you may have cooked it. In some cases when they're fried, they'll still emit some light (Like an LED), but it'll be very low power, and the diode will get very hot very quickly.

If it's a 5.6mm diode, put it in an Aixiz module and you're done.
 

JohnScolaro

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Ok, thanks! Ill order another diode just because I can, (only cost like $4) and Ill buy this module. Thanks! Will the laser disparate incoherent light, if it isn't in a module? Even if the laser diode is in perfect working condition.

It is a 5.6mm diode, so I'll get on that. Thanks again.

P.S. Australia FTW
 

Blord

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Hey guys, this is my first post, but I've been following this site for a long long time. I have finally ordered in all my parts to make a LM317 laser driver for my 300mw 808nm laser diode. And I connected everything up after testing, and all went well. The laser diode came on at an output of around 100mw, and continued to get brighter until I couldn't actually make it any higher at around 800mw input. (Which is ridiculously strong. But fantastic, because I'm looking for some solid burning action.)

The only problem is the laser diode seems to be emitting incoherent light, in all directions like an LED rather than in a coherent beam like a laser diode. I was wondering if most lasers do this, and mine just needs a casing, or whether there is something wrong with my laser diode.

How do I focus it? So it is in a beam, so I can get down to the burning part.

Please don't even mention safety, because i'm not new to electronics and lasers in general, just new to making them, and please dont ask why I want a burning laser, because obviously I want to burn things.

Thanks! :D
Not new to electronics and you mix power and current all together ? You should know the basic electronic laws. :tsk:

A 300mW 808nm is visually very faint and cannot be compared to a true red diode.
I know from experience that if you push this diode beyond 300mW it will turn into a LED.

Did you use a lens in front of the diode and how did you heatsink the diode ?
 

JohnScolaro

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I'll take a picture for you.

I didn't use anything at all. I feel like the vibe I'm getting from you guys is that I have blown it.

No heat sinking or anything for the diode, because I'm new to building lasers. I take it that it must be essential. :D

Thanks for the help by the way guys!
 

Things

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The light is still coherent, however it's just not collimated and thus spreads out.

When they die, one or both of the mirrors in the cavity are completely or partially destroyed (in the case of catastrophic optical damage, melting the bond wires is another failure mode)

Once the mirrors are destroyed, the laser won't lase anymore, instead it'll emit a faint glow.

Why not get a visible laser diode? It is very easy to become reckless with IR laser diodes as they are somewhat invisible to the human eye, however they'll still cause serious and permanent damage even though you can't see it.
 

JohnScolaro

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Simply because of the cost. When I get a working IR laser diode going. Then I will delve into the area of visible light. But I don't want to break any of those, when they cost about $50. So I am gaining some experience first.

And you're helping fantastically.
 

JohnScolaro

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Also, will I be able to see any of this damage with a microscope? Because I could have a look through mine.

Obviously not while it is on.
 

Things

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Possibly at extreme magnification levels, however the damage could also be on the back mirror, making it difficult to see. It could have also simply ablated the reflective coating off and not left a trace. So yes, you probably can, but it'll depend on a few factors whether you'll see anything worthwhile.
 
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JohnScolaro

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I don't really know what you mean by reflective casing, but I think you may mean the plastic which usually covers the top of the diode? If so my laser diode doesn't actually have one of them.
 

Things

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Reflective coating, ie, the mirror coatings on each end of the laser cavity.
 

JohnScolaro

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Thanks for the help! Could you possibly send me a link to the 5.6mm Aixiz module? I'm not sure I can find the one you mean.
 

jander6442

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Thanks for the help! Could you possibly send me a link to the 5.6mm Aixiz module? I'm not sure I can find the one you mean.
Get a simple 16x 660nm diode for the sake of simplicity... might save you the aggravation of not knowing intensity level judging from your eyes instead of a meter. In the OP it states 800mw I'm assuming you ment 800mA as the 800mW would mean you measured it with a LPM and I don't see you listing that fact.:)
 

daawood123

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PHR's and LPC diodes (405nm and 650nm respectively) are quite cheap, like $10. Much better than IR, cause you can actually see the beam, trust me, burning things with lasers becomes over rated after a while, you will soon get bored.
 

jander6442

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PHR's and LPC diodes (405nm and 650nm respectively) are quite cheap, like $10. Much better than IR, cause you can actually see the beam, trust me, burning things with lasers becomes over rated after a while, you will soon get bored.
NOOOOooo... I NEVER get bored of burning with lasers... I just run out of things to burn:na::eg::eg::eg::eg:
 




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