# How Do Lasers Burn Out?



## **DONOTDELETE** (Apr 19, 2002)

Does any one know how a laser burns out?

Does it start to gradualy get dimmer or suddenly burn out, or what?

Flashlightguy


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## lightlover (Apr 19, 2002)

Hi, Steve,
from my own experience, ...... delete delete delete delete delete delete delete delete delete delete delete delete.

Delete delete delete delete delete delete delete delete delete delete delete.

Craig will know ......
....... Ummm, on second thoughts, disregard what I might've said, and wait for Craig to answer.

lightlover :OOps:


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## The_LED_Museum (Apr 19, 2002)

A diode laser usually fails catastrophically.

Too much current causes the number of photons bouncing around inside to exceed the mechanical and thermal limits of the end facets, effectively blowing one or both of them off. End of laser. You end up with either a DELD (dark-emitting laser diode) or a very expensive, dim red LED if the P-N junction wasn't fried.





A _little_ too much current, excessive Vf or Vr; or the application of static charge to the chip causes what are known as "dark line defects", which are defects in the end facets that affect the beam quality and output power. This type of damage (actually, *all* types of damage in diode lasers) is irreversible once it has taken place; though its progression can be often be halted or greatly slowed by lowering the LD current to just above threshold.

In higher power diodes, contamination of the output facet can also cause various failures, ranging from simple beam irregularities to complete failure of the device when the contaminating particle smoulders or ignites, depositing carbon on the OC, and causing a type of failure similar to that seen in overcurrent situations - the end facet absorbing too much energy and being blown to smithereens by thermal stresses.

Cratering of the bond or failure of the die attach can also occur, but the diode usually blows up by one of the above mechanisms long before this can happen.

There are a lot of other ways a laser diode can meet its maker - some of them very complex and extending to the subatomic level; but these are the most common.


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## Marked (Apr 19, 2002)

The magic smoke leaks out and it stops working.

You know that electronics works on magic smoke, don't you?


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## Graham (Apr 19, 2002)

Ahh, magic smoke. Many a time I've let the smoke out of various electronic bits, especially back in college. Used to get old computer boards and zap them at interesting spots with a 12v or maybe 20v high current supply. Then watch the tops pop off the ICs..

The old line we used to use on people new to electronics and ICs - put 12v or so across a typical TTL IC, and smoke comes out. It doesn't work then, so the smoke must have been what made it work. Right?





But Craig - you've described about diode lasers. How about gas lasers? I've wondered about that myself..

Graham


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## The_LED_Museum (Apr 19, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Graham:
*But Craig - you've described about diode lasers. How about gas lasers? I've wondered about that myself..

Graham*<HR></BLOCKQUOTE>

The four most common failure modes in gas lasers are breakage, fill contamination, helium diffusion, and sputtering of the optics.

Breakage is just that. Drop a ceramic or glass plasma tube on the floor, and it will make a satisfying, sometimes loud "POP!", followed by the familiar tinkling sound of broken glass. That's the end of that laser. :-/ 
Best you can do now is to grab a broom & dustpan and sweep up the remains to feed the hungry, hungry garbage can. In some cases, the HR and OC optics are salvageable, but the rest is "put-a-fork-in-it" done. Knocking the end off a laser tube, knocking the stem seal off, or cracking the tube without breaking it will simply cause the tube to come up to air, and again, no laser. Cracked tubes can occasionally be resurrected, but they won't remain usable for long because the barium getter will have been exhausted when the tube filled with air.


Fill contamination is when atmospheric gases slowly infiltrate & contaminate the tube's gas fill, or foreign matter on the walls of the tube (usually tubes that were improperly baked off) sublimates and contaminates the fill. Most tubes have a getter electrode inside - a small metal ring, usually hollowed out and open-faced, filled with a compound composed mainly of metallic barium and a few other materials based on rare earth metals. During the final stages of manufacture, just before the laser's gas fill is introduced, this ring is installed. After everything's been sealed off, the getter ring is electrically or inductively heated, coating a small area of the tube wall near the getter with the vaporized metals. This is the shiny, metallic spot you see on the side of a HeNe laser or at the side or top of a radio vacuum tube. The getter combines with oxygen and other organic contaminants that happen to leach into the tube over time, or are inadvertently left behind after the baking process. When this getter material turns all white, it's been used up and the tube will then begin to poop out and eventually die as the internal gas pressure ever so slowly rises and the precisely-metered fill gases become diluted and contaminated.


Helium diffusion is a problem encountered mostly with helium neon (HeNe) and helium cadmium (HeCd) laser tubes; though any plasma or ion tube using helium as part of its mixture is vulnerable. Believe it or not, this type of failure is sometimes reversible, and with no special equipment required. Helium atoms are small little buggers, and they can and will percolate through the glass walls of the tube and diffuse into the atmosphere. This is why most HeNe lasers quit working after x number of years even if they were not used for many hours. If you catch it right at failure or before, you can sometimes revitalize them by putting the tube in a thick plastic garbage bag, squeezing as much air out as you can, and filling the bag with helium that you can get at your local party supply store. Seal the garbage bag off with rubber bands as best you can. Figure on leaving the tube in the bag for 1 day (or was it 1 week - have to look that up) for each year it is old, and expect to inject helium in the garbage bag as much as a few times a day while this is being done.


Sputtering is almost always fatal. It is normally caused by excessive tube current or reversed polarity. Material from the cathode literally sputters off the metal electrode and deposits itself on the tube walls and more importantly, on the mirrors themselves. Once this has occured, nothing can be done to fix it without breaking off the mirrors, replacing them, and rebuilding the tube as if it were brand new. Usually it's less expensive to buy a whole new tube than it is to have a sputtered tube refurbished; though refurbishing is a viable option if the tube is rare or is really expensive, such as those in large frame ion lasers.

There are other failure modes, but these are the most common.


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## TCPilot (Apr 19, 2002)

Craig,

Uh.....WOW.

Now THAT was a great lecture!!!!!!

/TCP


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## bronexx (Oct 31, 2016)

**DONOTDELETE** said:


> Does any one know how a laser burns out?
> 
> Does it start to gradualy get dimmer or suddenly burn out, or what?
> 
> Flashlightguy


 :fail: don't expose the diode to ambient particles!!!!!:tsk:...................... i cant stress it enough and one more important thing don't use an attachment if its not required im from LPF and trust me i know i have killed one Awesome GREEN laser when i added an attachment it was a life lesson and that life lesson is get yourself an lpm if you want to add an attachment AND DO SOME RESEARCH on the power output of the laser and see how high you can go in terms of voltage because if you don't you can cause a catastrophic failure witch can result in a dead useless laser it then becomes a host quote on quote useless until a new diode is found witch is the laser itself the heart and soul and as i mentioned with ambient particles a member on this comment has also mentioned if exposing the diode to ambient particles can cause a catastrophic failure by one of these nano particles getting into the diode and igniting its that simple the diode gets really hot diodes also have different temperatures depending on the watts or mw of the diode every laser has a certain cool down time that's why heatsinks and thermal past are sometimes added depending on the power there re also other failures that can take place but much more coplex take this comment and use it to your advantage thank you


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