Can a DPSS get better with use?

[IgorT]

Is it possible for the output of a green laser to become more and more stable with use? I heard something about a burn-in process, and was wondering what it is.


So far i had the same feeling with two DX200 lasers. Both were mode hopping, when i got them, and with both this seemed to reduce, the more i used them. They also both had abrupt brightness changes at first, but later it seemed to improove and happened less and less often. In both cases i kept changing the rechargable batteries, to keep them at full voltage, and i also measured the current, and it was unrelated to it.


Any thoughts? What exactly happens during the burn in process?

 

[Ace82]

"burn in" as apposed to "break in"? All I know is my RPL works best at ideal temp., not too cold, not too hot. I'm not sure about it increasing in strength, maybe it's the crystal, maybe it's the IR filter, what really happens when a laser ages? Good question. :-?

 

[bob12345]

I don't know about that but with almost anything involving stress and a deformable crystalline structure, there is a sort of "wear in". This is more of an adaptation though. A common example is a filament light bulb - if you have it running 10 years hanging top down then try to use it upwards, it will more than likely break there and then.

 

[IgorT]

You're probably both talking about the same thing.. I heard someone mention a "burn in" process in the S-KY group buy thread, which is why i used those words..

But it would seem, that it is not really improoving. In both cases i did some minor fixes, to remove some major design flaws, that could be remedied without taking the laser appart, which made it more stable.


But nothing really solves the problem completelly. I need to resist the temptation to take it appart and put it into a different host for improoved cooling. When this one mode hops, it first splits into two beams, then three and in the end four.


Need to... return... laser....

 

[bob12345]

I remember someone talking about a sort of burn-in process on the DX 30mW green forums, where you switch the laser on for 30 seconds, leave for a minute, then pulse it on and off for 30 more seconds. I don't know if that actually does anything.

 

[IgorT]

It does do something..

It cleans the switch a little and bends the "driver" PCB down even more, than it already is.

When i heard of pulsing the laser, i took the batteries out, and kept pressing the button.. Cleaning the switch this way actually helped a bit. Of course i put a piece of plastic under the "driver" PCB first, since pressure on the button actualy made it change modes.

With the first one i was able to get it back into TEM00 just by varying the pressure on the button. After i put the piece of plastic in, it became much more stable, but stil far from perfect.


This is a MAJOR design flaw in these pen lasers.. The driver could have a plastic sleeve, like leadlights, or it could at least have something glued on the underside of the PCB.

Another big flaw is, that the laser module doesn't even touch the outer shell. If you can feel it is warm from the outside, it must be scorching hot on the inside.


I just don't have any luck with the DX200 lasers. Rain at DX even tested this one for me, before shipping it, and they wrapped it in some extra bubble wrap, just like i asked.. But even tho he said it was "allways bright, no dark", the laser is almost blinking during warmup.

And when it mode hops, it first splits into two, then three and in the end five dots or so..


I can stop the mode hopping, by attaching it to a current regulated power source and setting the current just below the one when it hops. But i can't get rid of these brightness changes. Could be an electrical problem, but i don't want to risk taking it appart, in case it isn't.


Doesn't matter anyway. I'm sending it back.

 

[monel_funkawitz]

How in the hell are you guys getting this apart?

I heated the crap outta it, froze the end in nitrogen, and I STILL can't get that damn locktite to break loose.

 

[happytomato]

Thermite. ;D

 

[IgorT]

How in the hell are you guys getting this apart?

I heated the crap outta it, froze the end in nitrogen, and I STILL can't get that damn locktite to break loose.

It's hard to get appart, without damaging the silver paint on the head. You have to mount the head in a vice, so that the rest of the body sticks up, and then edge it out, by pushing and pulling at a 90° angle, forward and backwards, while also pulling it up.


If you twist it out, you will break the legs of the diode, since the button would prevent the PCB from turning with the module, and is directly soldered to the legs of the diode.. I've seen pics of the twisted and torn diode legs somewhere around here.


Oh, and realigning the crystals is not very easy. In the first one i just tightened the diode, and the brightness dropped to a pathetic level.  It took me a week to bring it back to where it is bright and doesn't mode hop.. But it's still not at full brightness. This will require alignment in front of a power meter, and it is still possible i might fail.

Once the diode or the crystals are turned just a little, there may be no way back.



After the bad experience with taking the first one appart, i am not repeating this. It is possible to get the laser module out, without it stopping to work, just don't mess with the diode or the crystals, unless you are willing to spend A LOT of time fixing it afterwards, with no guarantee it will ever get better. The chances are very low, because of the way it is designed. (no collimator or fast axis lens between the diode and the crystals)