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Can reflections kill a laser diode?

alessnilsen

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Hi! I was playing with my 650nm red laser, collimating and defocusing the beam, and, suddenly, my laser diode died!

Now, I want learn from this, but I can't understand why my laser died.

I was using a little lens from a DVD sled (the one with 6mm) and a big glass plano convex lens, the first one defocus the beam, and the second, collimate the light again.

Someone can explain this for me?
 



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Yes, I think it can. It's the same thing as pointing a laser in a window, the reflection can burn the diode, that's why high powered lasers like 445 1W uses AR.
 

grainde

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To be honest its more likely that you ran it too long, or that the current was simply too high for the diode. Just because 1 particular LPC 815 diode can handle 415 mA, it doesnt mean a different LPC 815 diode can.

Perhaps try a lower current on your next build.:beer:
 

123splat

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Google Catostrophofic Optical Destruction (or Damage). Power reflected back into the chamber causes thermal and physical shock to the die, resulting in chipping or deformation of the lasing surface.
,,, so,,, yea, it is possible.
 

alessnilsen

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That's sad to hear! :undecided: :yabbem:

If that's caused by overcurrent, will 375mA be fine? I wan't it to last long.

If that's caused by reflection, there's no much I can do about it.
 
Last edited:

BShanahan14rulz

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If you are careful, just be more conservative with your current. If you cut it in half, you are even less likely to suffer COD from light being reflected back into diode.
 

alessnilsen

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:)

I think I know what happened: the lense that I used is like this:


I was playing to see if have any difference if I unfocus the beam with the flat or the curved surface.

If I use the curved surface, the lens operates correctly causing a difuse reflection (because it's glass).
If I use the flat surface, the lens operates as a mirror, causing the powerfull collimated beam to reflect directly inside the laser, destroying it.

That's what I realised from this, I don't know if is correct.
 

Alaskan

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I put a laser line lens on a 2 watt 445nm diode and I suspect it died from the reflection off of that gradient glass.
 

alessnilsen

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Sad to hear this! I'll build a 1W 445nm, and hear that your 2W died makes me sad! :undecided: :cryyy:

Remember, if you mirror the beam again to the laser, the collimating lens will focus it exactly into the LD die!
 




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