Manufacturer statement regarding decanned diodes

[RedCowboy]

That's what I read as well, so without nitrogen, oxygen would not be needed......at least not for preventing nitrogen deposition, also I read before that oxygen itself could be a problem.

I wonder how well things would work in a vacuum vs. an inert backfill.

We could vent the can while listening for the sucking sound to 1st see if it's in a vacuum, also trial and error backfilling could prove successful.

Something that could make sense of the higher energy density aspect and the mention of micro fractures in the structure is moisture, if the facet absorbed any moisture it could be turned to steam faster than it could escape causing tiny damage and/or deposits. I would bet humidity in the air is a big factor in transferring contaminants as well, but the fact that reds and lower power greens last suggests the energy density is a big factor, so a clean inert environment may also be achieved by operating in a vacuum.

 

[paul1598419]

If I were going to use GC-Mass Spec to look at these failed diodes I would place several of them into a proper solution that would dissolve or react with these gases or particulate matter. The GC-MS I used in school would separate and identify very minute amounts of these elements or reactants. I'm sure it would be possible now as it has been many years since I last had to analyse small amounts of unknown substances.

 

[RedCowboy]

I know the damaged diodes still take full power and give less output with more waste heat no doubt, so we know damage happens, and yes knowing what the deposits are could help answer some questions but I think a more relevant question is how do we avoid it, I wonder if we installed a window can with indium foil seal possibly using an inductive loop to heat around the cans lip while inside a vacuum glove box, if that would restore normal lifespan, what's the feasibility of us using a backfill vs. a vacuum and would either work better than the other ?

I suppose the answer to using a vacuum is try and see, same could be done with inert backfills, also the window can could be sealed mechanically with a threaded lock ring and seal but as we can use the diodes with the GBall intact I bet that's the way it will go with a longer optical train.

 

[Benm]

If you were somehow to hermetically re-seal these diodes that'd all be worth trying. It doesn't really answer te question of what was in there in the first place, but it could rule out what the problem is: nitrogen, oxygen, water, etc?

The problem would probably re-sealing them though: how do you replace something like a lens or window so it's absolutely airtight? Especially when you have to do that in a controlled environment like a glovebox filled with argon or nitrogen to test if those would be problem?

 

[RedCowboy]

Use a new window can and an indium foil ring to seal it, you would liquefy the indium with an inductive loop made to fit around the window cans base/lip, this would be done in the inert gas flooded glove box or a vacuum glove box.

Or you could make a loop to fit around the window can from 12ga copper wire and attach to a 100w soldering gun to melt the indium foil gasket and seal the can, that's a better idea as the inductive heater could damage the laser but the soldering gun loop would be fine, you could even press it directly against the cans lip for a fast heating of the intended area.

 

[Benm]

That could be a way of repairing the diodes indeed, but it doesn't really answer the fundamental question: what are these enclosed laser diodes filled with to begin with, and why?

I think it would be mostly against dust, but perhaps also against oxygen or water vapour, though there are plenty of open case diodes out there that work just fine exposed to ambient air, but specks of dust can kill them quite easily. The dust problem is mitigated by operating the laser in an enclosed module though. If you put an a diode in an aixiz style module the dust is kept away by the lens, but oxygen and water can still get in there easily. This just moves the dust problem though, as it will cake onto the lens instead of the diode now. Generally this is good since the diode is often the more expensive part of the build, but still an issue.

 

[paul1598419]

This is the main reason why I store my lasers with lens caps and/or airtight bags as it is a lot easier to keep dust off a lens than to try to remove it later. It has worked out pretty well for me over these many years. As far as my sealed lab lasers go, I always have a piece of tape over the output aperture and never open them up unless they are in need of repair.

 

[RedCowboy]

I have many nubm06,08 diodes that wore out way early...well were changed out at half brightness after only a month of moderate daily use that were in a 12mm copper module with a lens and a beam expander, the daily focusing was all done with the beam expander and the diode was pretty well protected, yet still they all wore out very early.

Moisture/humidity and trace elements are likely a big factor but whatever it is I know it happens with only the air trapped in a 12mm module between the diode and the fixed/set lens.

I expect a vacuum or inert backfill is needed, we could try trial and error and test for results, but I expect we will use extra optics as I have done to use the GBalls intact at an additional 10% loss, that's the GBall plus a backwards G2, after that you use a lens as you would otherwise.

 

[paul1598419]

I recall reading some time ago about organic molecules causing damage to certain diodes if they are not sealed against them. So, carbon may also be a factor in damage to some of these diodes.

 

[RedCowboy]

Yea, that last bit I read by the German researchers found tiny cracks in the structure and that nitrogen alone formed deposits but oxygen kept nitrogen from making deposits, I also had read before that oxygen was part of the problem, so that leaves the trace elements. particulates, and moisture.......it could well be a combination effect of deposits and damage, possibly from moisture and trace elements.

I wonder about moisture after shutdown causing those cracks to grow, well again it could be a combination effect.

It seems that the damage only occurs while lasing, there doesn't seem to be any degradation while in storage with the can removed, not that we have noticed anyway.

Really it's all academic at this point, but still interesting.

 

[kecked]

Use dry argon. Nitrogen is actually reactive. The temp and energy at he facet is actually amazing. Water would easily ionize to form H+ and OH- hydroxide could be corrosive to any glass like material. I did some experiments in nitrogen and the diodes did die after a few months but not all. I still have one running for five months. I however have no moisture. I think O2 and N2 and H2O are contributors but trace chlorides sulfide and the like along with carbon deposits from incinerated dust are likely the reason they fail. End result seal your diodes in dry argon. Argon is heavy so it can take considerable time for argon to leech out and air to get in.

Build it in a box or bag purged with argon. If you use a bag watch for static. Plastic bags have a killing charge on them.

 

[logsquared]

Maybe we could get one sent to the ISS and we could schedule an EVA to test a diode in space vacuum. It might be hard to get the EVA? Maybe we could use the robotic arm to do the test. Then we could have a specially designed return vehicle made for the diode to be sent back to earth. The return vehicle wouldn't have to be too big. It would have to stand up to the heat of re-entry. Maybe made of diamond or something?

 

[Benm]

Interestingly in space you have other problems like increased ionizing radiation that could also kill a laser diode.

There would be no need to do anything like that to see how diodes behave in a hard vacuum though, plenty of methods to do that on the ground.

What i've found odd is that some diodes don't even have a can by design and seem to work fine (in optical drives and such), so it must depend on diode chemistry/composition as well has to how sensitive they really are.

I suppose using argon as a filling material would be fairly easy to do and obtain, but as a chemistry master i do wonder what reactions take place when using dry nitrogen instead. I can see how oxygen and water would do damage, but nitrogen is pretty inert to most materials, espcially ones i'd think you'd use in semiconductor construction.

 

[RedCowboy]

10W+ C-mount IR diodes are common and are open, so I have to think it's the structure that's reactive or susceptible in the case of our favorite blues. Yes I know the C-mount diode is used in a closed environment, but it is surrounded by air.

https://www.ebay.com/itm/808nm-15W-High-Power-C-Mount-Laser-Diode/251032473102?_trkparms=aid=333200&algo=COMP.MBE&ao=1&asc=55164&meid=da3be79dea8f45229ee899af83079fb6&pid=100752&rk=1&rkt=12&mehot=pp&sd=251167378824&itm=251032473102&_trksid=p2047675.c100752.m1982

 

[laserdave10]

Apparently not - as goes with so many things in asia. You'll often find even things like restaurant menu's printed on very expensive material containing blatant spelling and grammar mistakes that even a non-native speaker would easily spot.

But when it's in a technical document like this it also makes me wonder if they have taken any care to present the correct information at all. I presume this was translated from kantonese or mandarin into english by someone that, apparently, does not speak english all that well but at least made the effort.

The main problem is that it does -not- really say what could cause the damage. Hermetically sealed package is fine, but what is contained inside? Is it in dry air, a vacuum, argon, nitrogen, sulfur hexafluoride, or perhaps something totally different?

It's feasible that the chip could be damaged by oxygen from the air, but also that it's not. Things like water vapor or dust are also likely contaminants that could kill it.

I remember the transistors in metal can bodies. Those worked just fine if you opened the can, but circuits would go haywire due to -light- getting in and turning them on. The transistor chip itself was perfectly fine exposed to air, but became essentially a photo transistor that just turned on when lit, regardless of any base drive current

For anyone interested, I found this paper that discusses what happens to the diode output facet under the influence of oxygen, water vapor, and nitrogen. From the Osram laser group in Germany.

 

[kecked]

Looks like water vapor is the main issue. Nitrogen could be depositing nitrides on the surface that burn off as show in nitrogen. Nitrogen is very reactive. My take away is you need ultra pure ultra dry argon or neon or helium To seal the can. I’d go argon as it is heavy and less likely to escape And cheap.

edit…well good to see I remain stable in my thinking. Didn’t see my response from 2018 till I read the paper and posted this response. Guess I was right.