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What do the Different Patterns Mean on the Raw Output of a LD Mean

kuhny1

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Hey everyone,

So I've been messing around with lasers for only about 2-3 years and i have noticed that on some of my diodes i get different patterns. I understand that on 445nm lasers that the output is rectangular with bars, and 650nm have a nice circular output.

But sometimes on the diodes I bought, I have noticed swirls on the raw output. Granted, my red laser diode has its' window shattered but its still operating just fine even though its filled with broken glass rattling around inside. However, my new and unshattered 445nm 1 watt diode has these swirls on the bars.

Any idea what they mean, or does it show rapid LD degradation?


 
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DTR

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The diode window has had some minor dust particles land on it. I would clean it and see if it gets it off. The issue is to the center slightly to the left but it is reflecting scattered light all over the place which is the haze you see all over. Give it a good cleaning and see if it goes back to a nice clean bar.:beer:
 

kuhny1

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The diode window has had some minor dust particles land on it. I would clean it and see if it gets it off. The issue is to the center slightly to the left but it is reflecting scattered light all over the place which is the haze you see all over. Give it a good cleaning and see if it goes back to a nice clean bar.:beer:

Thanks for the reply,

I have wiped the diodes' window but nothing happened, I guess it could just be a imperfection in the glass because it was a cheap diode ($16, part number NDB7412T). Even for that cheap it seems to run happily at 1 watt :yh:
It doesnt really even get that warm, but it might just have good heat sinking on the host. We'll see how long it goes before it pops :evil:
 

DTR

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If it will not clean it is probably burned in the window at this point. How did you try to clean it? I usually use a Q-tip and some 97% Alcohol. Rub with the wet side then the dry and blow with compressed air in a fairly quick succession.
 

kuhny1

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If it will not clean it is probably burned in the window at this point. How did you try to clean it? I usually use a Q-tip and some 97% Alcohol. Rub with the wet side then the dry and blow with compressed air in a fairly quick succession.
OK I will try that thanks :)

One question, can this cause a premature diode death because of the reflected light?
 
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Maybe... It depends on how much reflection, and if they come directly back to the diode.

I have seen some who used a perfectly perpendicular mirror to accidentally kill their diodes.
 
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Thats definitely dust on your diode window. Nothing to be super concerned about. If it bothers you then you can try to give it a clean with some 99% acetone. I recommend using a Q-tip and giving it a little swirl while going over the window.
 

Gabe

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Maybe... It depends on how much reflection, and if they come directly back to the diode.

I have seen some who used a perfectly perpendicular mirror to accidentally kill their diodes.
Hey, wanna see my 300mW 650nm laser? Oh wait... ;(
 




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