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Rofin DPSS YAG metal cutting laser teardown

RedCowboy

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I would bet the mirrors are enclosed in the end structures.

I would like to see the pump diodes from the output end also.

With 4 strings each driven at 42v and 50a that's 8000w input power, maybe 4000 out of the pumps and what ???? 500-1000w out of the rod ?

If 7000w of waste heat it no doubt needs a chiller, I wonder what the normal operating temp is ?

You could power just 2 strings, one on each side at reduced power with a deionized water loop, but I would monitor the water temp, and get some proper eye protection first !
 
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paul1598419

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I would like to get an idea of where it originally came from as there are too many variables here. Would like to see those photos too. I have a feeling this was a powerful laser once. I wonder what its intended purpose was.
 

diachi

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I would like to see photos of every aspect of this Nd:YAG. I'm not so sure it is without mirrors, but can't tell from the little bit I've seen so far. I still think it was a hell of a deal for the price.
Red beat me to it, but there may be mirrors in those end structures.

I would bet the mirrors are enclosed in the end structures.

I would like to see the pump diodes from the output end also.

With 4 strings each driven at 42v and 50a that's 8000w input power, maybe 4000 out of the pumps and what ???? 500-1000w out of the rod ?

If 7000w of waste heat it no doubt needs a chiller, I wonder what the normal operating temp is ?

You could power just 2 strings, one on each side at reduced power with a deionized water loop, but I would monitor the water temp, and get some proper eye protection first !
Agreed on the mirrors.

Your power numbers add up too, although I wouldn't expect to see quite as much as 1kW out at 1064nm. That'd be some seriously impressive efficiency. I'd expect anywhere between ~10% and ~20% optical efficiency (400-800W).

I would like to get an idea of where it originally came from as there are too many variables here. Would like to see those photos too. I have a feeling this was a powerful laser once. I wonder what its intended purpose was.
Also interested in that information. That much power has a lot of applications, especially if there was originally a Q-switch involved.
 

paul1598419

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I agree with your optical efficiency, but I doubt it had a Q-Switch unless it is hidden in the end structure. From what I have gleaned from Koechner's book, an AOM Q-Switch for a CW pumped Nd:YAG laser would take up more space and have a different optical setup than what I see here. I don't think it would have a passive Q-Switch as they have been shown to be less efficient with an end pumped rod like this one. So, unless there is one hiding in there somehow, I don't think so.
 

diachi

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I agree with your optical efficiency, but I doubt it had a Q-Switch unless it is hidden in the end structure. From what I have gleaned from Koechner's book, an AOM Q-Switch for a CW pumped Nd:YAG laser would take up more space and have a different optical setup than what I see here. I don't think it would have a passive Q-Switch as they have been shown to be less efficient with an end pumped rod like this one. So, unless there is one hiding in there somehow, I don't think so.
I don't see anywhere for a Q-switch either. If there's mirrors in those end structures that rules one out as there'd be no space for an AO Q-switch.

Q-switching isn't ideal for metal cutting either, if the title is accurate. Q-switching is better suited to engraving/etching. CW makes more sense for cutting.

The setup isn't much different for an AO Q-switched YAG though, just need to move one of the mirrors a little further away from the end of the rod and drop in a Q-switch in the extra space.
 

RedCowboy

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I agree with your optical efficiency, but I doubt it had a Q-Switch unless it is hidden in the end structure. From what I have gleaned from Koechner's book, an AOM Q-Switch for a CW pumped Nd:YAG laser would take up more space and have a different optical setup than what I see here. I don't think it would have a passive Q-Switch as they have been shown to be less efficient with an end pumped rod like this one. So, unless there is one hiding in there somehow, I don't think so.
You meant side pumped ?

It looks like the pump diodes fire through the slots in the cavity and the coolant runs around the rod inside that clear sleeve, an interesting setup.




The coolant appears to enter and possibly exit through those 2 blue O-rings, maybe that clear cover is a tube inside a tube for the return coolant, or they could be dual cool water inlets and the heated water could exit through the output mount after flowing through the tube around the rod. I see blue and red O-rings I suspect for inlet and outlet coolant.

Although the diode blocks would need cooling as well, so maybe blue for the rod and red for the diode blocks. But I don't see any way for it to be end pumped.




There are pics here of the whole unit.

https://www.ebay.com/itm/ROFIN-SINA...m=362291519246&_trksid=p2060778.c100290.m3507


Interesting note, it appears that Coherent bought out Rofin, Nufern, and Dilas but are keeping them as separate entices in the coherent family. > https://together.coherent.com/


.
 
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paul1598419

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I didn't realize it was in several pieces. If that is the case it would be side pumped. It still isn't clear from the photos how the diodes' output is coupled to the YAG rod, though. That is what is difficult from looking at a few photos that aren't terribly clear. I am just going to wait until I can either see better pictures of the assembly or someone comes up with a manual or description of this laser.
 
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RedCowboy

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You can see the slot on the top side as the diode string is pulled back, it would make sense to keep as much of the reflector as possible.

It would be nice to see more pics.

Looking at the Ebay pics I see coolant connections at what looks like those rod end mounts.

 
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Alaskan

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I'm not sure what I'm seeing there, what is that strip being pulled back, copper contacts? What are the individual brass pieces under it with some of them missing? Cooling contacts?
 
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This should answer a few questions:

First, diodes. They are standard bars on submounts, microchannel cooled.




They have thin gold(?) strip as a negative contact

Second: rod with flowtube goes in there. Cooling paths are all connected.



Third: There are no mirrors in mounts at all, so unless rod ends are coated (which I doubt, colour doesn't seem right) it needs external mirrors. So I probably could even make a yellow laser as powerful as NASA starguide using two such units if I just had the right optics.



Also the seller provided a factory test sheet for it but I can't find it anywhere. Anyway it produced a bit over 1kW output power at full current (probably 1064nm)
 

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DashApple

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The diodes effectively sit around the rod and just dump light into it , the chamber is probably made so that the diodes sit close enough to the rod so that as much light as possible hits the rod .

Its the same as the doughnut diodes you can get but in the case they are using single bars
 
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diachi

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Power test:

I hope it was decomissioned just after this test and still has the same amount of hours :yh: There is a fair chance its true: note on bottom says "only for used condition" - decomissioning?
Damn, that's some serious power!

Looks like it was a module intended to be mounted on to a larger optical deck. That means Q-switching and external mirrors should be "easy" enough to set up! Maybe talk to Laserbuilder (https://laserpointerforums.com/members/laserbuilder/), he has experience with YAG lasers at those sorts of power levels.

Make sure you don't get any contamination on any of the optical surfaces. At these sorts of powers the intracavity beam will surely cook any contaminated optics in an instant...
 
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paul1598419

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850 watts at 34.9 amps. I'm impressed. Like diachi said, keep the optical cavity clean and clear of debris. So, this was made to cut metal. Very nice find. Especially if it needs little to resurrect it.
 
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Well, I've decided to buy a second one and use first one with 3 diode blocks (one has been irreversibly dismantled) for my future project, gonna start building power supplies now - I'd probably buy several telecom 48v high current supplies of the same type (present on my local auctions site) and think about making a two stage chiller (radiator+fan as a waste heat dump, TEC block after it to precool water to set temperature) . Anyone knows how to make a chiller for things like this? Also how I can determine the correct coolant pressure? Also, I've determined that there are surplus optics on ebay suitable for this kind of power (for making a 532 laser) so let's make a damn deathstar
 

Laserbuilder

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Hello

Here I'll show a typical russian chiller for a lamp-pumped 250W YAG laser. The tank is filled with distilled water that is pumped into the water jacket of the YAG rod with the pump on top of the tank, and through the coils of tubes cold water from the tap flows to take away heat from the first loop. The second loop can be closed too in case you use a big fridge to cool down water in it. This unit is capable of taking away 5 kW of heat. Continiously.

And yes, this is a great laser. It would be cool to make 200W of green ot of this amount of IR))) Or 50W of red. +rep
 

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