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Manufacturer statement regarding decanned diodes

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When I was reading the datasheet for the Sharp GH04850B2G I came across this declaration in the notes at the bottom of the document-

seal.PNG

At this point it was pretty much accepted that decanning InAlGan diodes resulted in a quick death but this is the first confirmation that I have seen from a manufacturer. Just FYI :)
 

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Love reading translated manuals. That is a very mild example of some of the things I've read. Does no one proof read these documents? LOL
 

paul1598419

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This just confirms what we've already seen here. I wonder why they felt the need to add this disclaimer as the diodes are made for specific uses by the end product manufacturer.
 

Benm

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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 :D
 

diachi

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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 :D
AFAIK the can often contains an inert gas. What that gas is I couldn't say.
 
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The main reason for the diode can is the protect the diode from water and dust particles that would stick on the diode facet and destroy the diode in the longterm. This is even worse for high power diodes because the beam creates an optical tweezer that pulls small particles to the point of the highest density, the diode facet...

I know that dry nitrogen is often used in laser diodes as an inert gas (cheap and easily manufactured) but some NIR need also some oxygen to react with some products before they can react with the diode itself. If somebody wants to "seal" open diodes I would suggest dry nitrogen.


Singlemode
 

paul1598419

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It is strange that the ML501P73 diode is made as an open diode. I do see the tweezer effect as this can be seen at the beam waist as well. I have one of these diodes doing a bit over 1 watt and it is about four years old now and still going strong.
 

Benm

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AFAIK the can often contains an inert gas. What that gas is I couldn't say.
The problem is with -inert- , which is a relative term. Air can be considered an inert gas to many substrates: most things we use in everyday use do not catch on fire when just exposed to air, and hence air could be considered an inert storage medium for something like a wooden table at room temperature.

So we don't really now what the problem is when these diodes are decanned: is dry air a problem due to oxygen content, or is it something like moisture in the air, perhaps water vapor?

I doubt the optical tweezer effect dragging in particles would be that significant on an expanding beam from a bare diode, but just small dust particles from ambient air might be problematic as the bake on the facets easily. Even with canned diodes you sometimes get dust to bake onto the output window with hardly any feasible method of getting rid of that.

I guess if the manufacturer doesn't state what component of air is damaging the only way to find out is to de-can one in a cleanroom, exposed to oxygen but not dust or significant amounts of moisture, and see if that actually kills it or not.
 
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It is strange that the ML501P73 diode is made as an open diode. I do see the tweezer effect as this can be seen at the beam waist as well. I have one of these diodes doing a bit over 1 watt and it is about four years old now and still going strong.
The similar reliability of as-manufactured open can diodes to closed can diodes suggests that it may have nothing necessarily to do with dust particles and everything to do with some other component of air degrading these device which doesn't have the same degredation on red diodes... either oxygen, trace gases or humidity. It doesn't seem that a decanned NUBMXX diode holds up even if it's decanned in a dust free enviornment then put in to a clean module with tight fitting threads. Not to say that dust is harmless to open can diodes but rather it seems that simply having exposure to air is harmful to InAlGan diodes.

The datasheet also mentions this
sharp note.PNG

so apparently the product doesn't do the design that intends use in the, special environment where a lot of moisture exist. Or something like that ;-)
 
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You might read this https://www.researchgate.net/public...gradation_of_GaN_heterostructure_laser_diodes
Or a short abstract
We investigated the degradation of cleaved facets of (Al,In)GaN laser diodes in different atmospheres. We found that operation in water-free atmospheres with sufficient oxygen shows a slow degradation. Operation in atmospheres with water vapor causes a fast degradation and an oxidation on the facet. This deposition is a permanent damage to the laser diode. If the laser diode is operated in pure nitrogen, we find a thick deposition on the facet, which shows high absorption. This deposition can be removed by either high optical output powers or by operation in atmospheres with sufficient oxygen. We also explain the influence of these coatings to the degradation behavior and see these coatings as the reason for unstable kinks in the L-I characteristics during operation.
I think it gives ideas what might happen to an exposed laser chip.

Not clear air - dust, aerosols - are another no-no for lasers.
 

paul1598419

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That was an interesting article. I especially liked the electron microscopy image and the SEM images. It seems that the Germans are always doing research like this as I have read several papers related to facet degradation over time.
 

RedCowboy

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It may be the energy density, the entire output occupies much less that the full face of the facet, the p/n junction behind the facet is just a slot. So far my 1w 520 de-canned diodes are still putting out full power and that may be due to the lower energy density.

Here's a pic I took at an angle and focused to show what I believe to be the junction through the facet or it could be damage at the output but as I adjusted the focus on my scope it came in and out of focus as the facet became more transparent, this is a de-canned nubm06 with a few hours total runtime ( est. )

In the 2nd pic you can see a tiny black spot where my camera is overdriven showing that junction, I have seen this in other images as well.

The 3rd pic is at low current.


1kxnubm06a.JPG
nubm06raw4.JPG
0921-6.jpg
 
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RedCowboy

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Ok I am double posting because of the time between. ( 1 week )

So is it moisture in our air along with contaminants that reacts at the facet when the energy density is high enough ?
Is oxygen a problem or is it preventative ? I had read before that oxygen was part of the problem.
This further makes me think there would be a backfill although what problems would running in a vacuum cause ? It might be difficult to get all contaminants out without a backfill, remember how vacuum tubes used a ( getter ) to burn up remaining oxygen, I don't thnk that would work here so a backfill seems more likely.
 
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Moisture is a problem for shure, along with dirt. At least for GaN laser diodes oxygen seems to be needed for preventing a reaction of nitrogen and the facet.


Singlemode
 

Benm

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I think it's mostly dirt/particlates at this point though.

If oxygen would be the thing killing these diodes it doesn't really make sense on how long they actually last when exposed to air.

It's hard to tell though, these laser diodes are so small it would be very difficult to get a sample of what gas in inside them from the manufacturer. Normally it would be possible to look at this using gc/ms, but the volume of gas is so small i doubt it would be possible to get it into a spectrometer without any leaks.
 




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