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another laser death.

Richie89

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this really sucks because i dont know what happened, i was making a bet to my girlfriend that i could crack a glass cup with nothing but light. I told her that since glass is transparent and doesnt really absorb energy well that it would take a lot of power but i could do it. so after firing my 2.1W M462 on it with it finely focused of course nothing, so then firing my NDB7875 2.8W and M462 at the same point at the same time and boom, I heard a faint crack sound and after shutting them both off i noticed the crack which was small, about 5mm wide but i did it! so i decided to see if I could crack it even more so I turned them both back on for a second run noticing that it definitly cracked agan. I of course let them both cool down almost cold to the touch, a 3rd time to crack it more and as soon as i turned them both back on I happen to see that the M462 was dim, i figured the batteries were dead since i havnt charged it in a while, as soon as i tried some fully charged batteries it was still dim, even trying 2 more new batteries and nothing, dim again.
i honestly dont know what happened. I know for a fact that I kept it under 45 seconds each time even making sure that the laser never got hot at all.

I believe I read somewhere that laser light could not re-enter the diode or it could damage it? does anyone think it was possible that the glass reflected the two lasers back in through the diode window causing the laser to get over loaded? I hate the fact that I destroyed another laser but if i knew what exactly happened I would feel a lot better and possibly not make the same mistake. thanks for the input everyone.
my apologies for sometimes not being able to respond back for up to a day, I have a very off the wall schedule.
-Richie
 

diachi

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Yes, back reflection can and will kill laser diodes, especially higher powered ones. Causes catastrophic optical damage.
 

Ivansuper

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That is really sad to see.
Well, playing with highly reflective surfaces is not only bad for your eyes, but also bad for your lasers. I had one destroyed almost the same way.
The light from a diode can definitely get back to the diode if being reflected "properly".
In this case nothing good may happen. In lucky case you get a slightly brighter output. In other case you get a LED instead.
Also, getting the light reflected back into the diode you may force it to start lasing at a current that is lower than a diode's threshold current. So that is it.

I do really hope you won't lose any more lasers in the future.

diachi was faster than me though : )
 
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probably a back reflection from the cracked glass,although the glass is transparent if it breaks it can make reflections of any way.
if a strong relfection hits the laser the lens of it focus the light back to the emitter and burns the diode itself

edit:Ivansuper i don't see how you can increase the output from a laser from back reflections as the only thing you will achive even if you don't burn the diode will be higher temperature on the emitter which will cause lower output not higher.
and your talking about "you may force it to start lasing at a current that is lower than a diode's threshold current" makes no sense to me as again threshhold current gets higher as the temperature gets higher.
 
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Ivansuper

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deadshadow,

This will happen when the light goes back to the diode's cavity. Diode emitter is not something black that will burn in any way.
"Increased output" doesn't mean that you will be able to get a more powerful beam. Instead, you will end up with somewhat external cavity diode laser with a higher power level inside it.

Edited:
But yes, when we are talking about big output powers, one would probably burn the diode before getting the light reflected back into the emitter (which will also kill the diode, as diachi mentioned)
 
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CurtisOliver

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Sorry to hear that Richie. Next time you try an experiment like that. Aim the laser so at 30-45 degrees to the glass so that you get reduced back reflection.
I killed a M140 once by trying to refocus the lens. The internal spring had moved and got in the way and caused internal reflections.
 
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Gazen

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Probably a reflection. Have you tested the current draw to make sure the driver is ok?
 

paul1598419

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It is impossible to say for sure what killed the diode. These are all overdriven, and the more so, the more likely it will fail prematurely. It is just as likely that using these lasers over and over again to try to crack the glass caused the COD. I try not to use the same over driven laser many times in the same brief period. Sorry for your loss, Richie.
 

Shotgundrums

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Sorry for your loss, buddy :(. Not a very cheap diode either... she’ll just have to sit out until you can get another one. 462 is a really nice blue too.
SGD:beer:
 

Richie89

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Yes, back reflection can and will kill laser diodes, especially higher powered ones. Causes catastrophic optical damage.
yeah that's what I was afraid of, I sure hope I learned from my mistake. lol
Sorry to hear that Richie. Next time you try an experiment like that. Aim the laser so at 30-45 degrees to the glass so that you get reduced back reflection.
I killed a M140 once by trying to refocus the lens. The internal spring had moved and got in the way and caused internal reflections.
oh dang Curtis :( I wanna try it again but like you said, at a 30-40 degree angle. hopefully all goes well :D
Sorry to hear this Richie :(

Light a candle, one more dead soldier.
:can: :can: :can:
thanks bob :) funeral will be held Friday 20th of April :crackup:

Probably a reflection. Have you tested the current draw to make sure the driver is ok?
I actually have not but that will be my next task because i wanna see if the driver is still ok, perfectly good X-drive :D

It is impossible to say for sure what killed the diode. These are all overdriven, and the more so, the more likely it will fail prematurely. It is just as likely that using these lasers over and over again to try to crack the glass caused the COD. I try not to use the same over driven laser many times in the same brief period. Sorry for your loss, Richie.
im gonna have to take that in consideration because youre right, it was a bit overdrivin im sure, so I could definitly see a premature fail. i just wish it would have been a cheap M140 diode.
Sorry for your loss, buddy :(. Not a very cheap diode either... she’ll just have to sit out until you can get another one. 462 is a really nice blue too.
SGD:beer:
hey SGD, yeah it definitly wasnt cheap, good thing it wasnt a 1W 520nm, lol!
i certainly have big plans for that MX900 host though, im thinking ill finally start a M44 build :wave:
 

paul1598419

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Sure. If you are just doing an experiment that isn't wavelength dependent, use the cheapest diode build you have. Then if the diode fails it doesn't hurt so much. :eek:
 

Richie89

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Sure. If you are just doing an experiment that isn't wavelength dependent, use the cheapest diode build you have. Then if the diode fails it doesn't hurt so much. :eek:
Hah! Yeah that’s true, what I should do is buy a stock pile of A or M140’s.
 

Richie89

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That's what I would do. They have gotten so cheap you will hardly notice if you blow one.
haha yeah its crazy to see how cheap they've gotten even since I started this hobby in may of 2015. thanks for the "just because" rep :)
 




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