NUBM44 6W+ 450nm Laser Diode

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^It would seem odd to not have enough leeway on the glass. I would like to see a diode run at 5A for a decent amount of time with no lens if this keeps happening. Are we absolutely certain there isn't too much reflected light back onto it? I'm certainly no expert, just throwing it out there. Is that glass absolutely clear with no coating on it? Wish I had the $ to try some things out to help but I can't afford to potentially blow that much Seriously thank you all for going through all the testing and talking it out right here in the forum so we can all follow along:thanks:

I agree, really appreciate all the folks doing testing on this and providing such detailed feedback.

I am waiting for things to settle down a bit with this diode, before even thinking of doing anything with it :bowdown:

 

[TaterMay]

I strongly agree. These diodes may seem bright, but the laser intensity of the highly divergent beam is no where near the typical damage threshold for CLEAN optics. A reasonable number for this is 100kW/cm^2. That is 1kW/mm^2. If the window is 1mm from the face of the crystal then based on the fast and slow divergence of other 445nm diodes,I believe the spot on the window would be about 0.1mm^2.

A small particle of dirt or absorbing film can raise the local temperature to the point where the particle or film carbonizes or smokes, thereby increasing the absorption and so on.

I also strongly agree with this. We have 16 4kW Trumpf lasers here at work. They have AR coated cover glasses in place to prevent any contaminants from getting on the five optic cables. There are three 1,333+ watt beams that are brought together passing through the glass all day(not continually; off and on), 6 to 7 days a week. The only time maintenance has to change these cover glasses is when debris gets on them and causes it to burn the glass. And this is with 900+nm(we use a few different IR wavelengths) diodes, which, correct me if I'm wrong, are absorbed by pretty much all materials much better than the visible wavelengths. So I highly doubt the glass is causing the issue without being contaminated somehow. I just had an NDB7875 burn a hole through the window. I believe it was caused by some debris from a heatsink with some TINY particles from the machining process. It happens. When you are dealing with such a concentrated beam of energy, even the tiniest of particles can cause serious problems.

Edit: Link to image of my NDB7875(less than half the power of the NUBM44) that I burnt the window on. I look at each diode under a microscope just before I power it up, and it appeared to be 100% clean. I really don't think these diodes are anywhere near the power threshold required to burn clean glass.

 

[RedCowboy]

Looks like a heat fracture. Did it give out while running or when you first turned it on after having the lens out?

 

[TaterMay]

After switching the 3-element lens out for a G2. Upon inspection, there were a fair amount of TINY particles in the threads of the module.

 

[RedCowboy]

After switching the 3-element lens out for a G2. Upon inspection, there were a fair amount of TINY particles in the threads of the module.

Yes I understand, but in the interest of sharing knowledge can you tell us if it was messed up the moment you turned it on after having the lens out or did it fail in the middle of use after you turned it on and it was working just fine?
Mine for instance was cracked the moment I turned it on after having the lens out twice this last week on 2 different diodes in high humidity. I think it was rapid temp change fracturing due to high humidity in an air conditioned room. That's not to say things can't get burned onto the window, I have seen blotches in the raw output where something tiny is stuck to the glass. But dead center fractures are looking like rapid temp change shock. I have pics up that look just like yours.

 

[planters]

When I inspected the NUBM diode window it had produced a faint yellow reflection. This is the same as the G9 lens and similar to other blue, anti reflection lenses I have in stock. I'm pretty certain the window is coated. The highly divergent beam reflected by the flat window will continue to diverge as it returns to the diode face. It is unlikely the retro-reflection from an AR coated window would damage the diode.

Although I'm also pretty sure the window failures will be contamination related, you could try a test. Run a relatively inexpensive M-series diode at a watt or so and then spray the window with some canned air. If this doesn't break it you could actually dip the front of the can in distilled water while the laser was running. My bet is that it won't break, but I may be wrong.

Interestingly, the very high end optics manufacturers take into account the tiny spherical aberration these thin windows generate in the divergent beam and the collimating lens is designed for either a windowed or window free diode.

 

[TaterMay]

When I inspected the NUBM diode window it had produced a faint yellow reflection. This is the same as the G9 lens and similar to other blue, anti reflection lenses I have in stock. I'm pretty certain the window is coated. The highly divergent beam reflected by the flat window will continue to diverge as it returns to the diode face. It is unlikely the retro-reflection from an AR coated window would damage the diode.

Although I'm also pretty sure the window failures will be contamination related, you could try a test. Run a relatively inexpensive M-series diode at a watt or so and then spray the window with some canned air. If this doesn't break it you could actually dip the front of the can in distilled water while the laser was running. My bet is that it won't break, but I may be wrong.

Interestingly, the very high end optics manufacturers take into account the tiny spherical aberration these thin windows generate in the divergent beam and the collimating lens is designed for either a windowed or window free diode.

I have also noticed what appears to be an AR coating on all the 445 diodes I've used. I can't really say exactly when it went bad. I just suddenly noticed the beam wasn't focusing correctly. I had powered it on for 15 seconds or so before I noticed it I believe.

 

[Alaskan]

The thought occurred to me to try to break the glass window on my NUBM44, but it is so close to the diode inside I fear I would easily damage it, I guess you got away with it but I bet you are lucky, most would just kill the diode doing that, I think.

Looks like a heat fracture. Did it give out while running or when you first turned it on after having the lens out?

When I looked at the burned spot on my NUBM44 it had a fracture in the window too. I bought mine 2nd hand from another member here and saw a problem with the beam when I first turned it on.

 

[RedCowboy]

The thought occurred to me to try to break the glass window on my NUBM44, but it is so close to the diode inside I fear I would easily damage it, I guess you got away with it but I bet you are lucky, most would just kill the diode doing that, I think.

I thought DTR was going to decan it for you? He has a tool made for just that.

 

[Alaskan]

I was going to try to do it myself, just don't have the tools delivered in the mail yet to pop it out of the copper head it is in.

 

[Pman]

Great investment is the entire set of presses and the diode extractor. I realize people look at it and think "I could buy a nice diode for that price but like all the other meters, soldering and tools there's nothing so nice as owning quality equipment to work with.
I can certainly understand the heat/humidity as a factor but unless something has changed in the manufacturing process I would have expected to see this issue being a live wire for quite some time as some of these diodes have been out long enough for this to rear it's ugly head.
Have any of the diode exchanges been tested yet?

 

[RedCowboy]

Great investment is the entire set of presses and the diode extractor. I realize people look at it and think "I could buy a nice diode for that price but like all the other meters, soldering and tools there's nothing so nice as owning quality equipment to work with.
I can certainly understand the heat/humidity as a factor but unless something has changed in the manufacturing process I would have expected to see this issue being a live wire for quite some time as some of these diodes have been out long enough for this to rear it's ugly head.
Have any of the diode exchanges been tested yet?

---edit---
It's a year later and I have half a dozen nubm44's working now and working well so it appears that I contaminated the window of that original diode, I would still avoid unnecessary thermal shock but after half a dozen more NUBM44's I have had no problems with windows.
It's a matter of user error in any case, we have to keep our diodes clean and dry, especially as the power level goes up.

 

[starlight]

Re tested mine tonight. I finally got the chance to move my diode from the copper 12mm module and into one of DTR's XYZ heatsinks. The diode seems to sit steady right above 7 watts for the 3 tests I did. All the tests we're about 45 seconds.

Did a quick video of last test. I get over 7W using 4.5A

 

[planters]

I got back from a trip this afternoon and DTRs diode had arrived. He also sent his mount and heat sink. These are nice quality and were easy to work with. The lens he sent, I am guessing is a G2 in a 9x 0.5 barrel. I added a small amount of PTFE tape to stabilize the focus and set it up. The bad news is the video I did was with a bad diode. The good news is the diode he sent performs as I had hoped and like most of the other testers have measured. At 600mA I was already getting 600mW. By 1,100mA, I saw 1,500mW. At 2,000mA the diode was producing 3,200mW. The maximum power was 7,100mW at 5,100mA. After this, the power began to drop with additional current.

The beam was better as well. With a 5x cylinder pair the beam at 30cm from the collimator was 7mm high and 3mm wide and at 14M the beam was 16mm high and 6mm wide.

As I posted above, my power meter is very similar to DTR's or around 5% conservative. In addition, I examined the lens he sent and it was pretty clean but, not perfect. It was in about the same condition as the G-9 that I installed for the first test.

The high power is a great finding, but the better beam is more important to me. Three of these could be knife edged to produce a 7x9mm beam with 20W of power and a PBS would allow you to produce the same beam with 40 watts!

Nice.

 

[DTR]

Great results on the retest and sounds like good news on possibly getting a useable beam out of the diode as well.

Glad you liked the XYZ mount. They really are very efficient at managing heat and this diode really seems to work very well in the mount. Looks like starlight's video above showed a radical improvement when mounted in the XYZ unit over his test with the diode just in a copper module in a small finned heatsink.

 

[Pman]

Now that is great news! Not only is DTR's LPM working fine but his mounts are really good and at least some diodes will hit 7W+ when pushed.
DTR have you tested thsee diodes with that heat-sink that was made for Mohs XML T-6 vs. the same heat-sink that has a regular 12mm module hole? For those who don't know it looks like this:

From what Starlight saw that sink should work pretty well if someone is looking for a handheld for it. If members are interested an all copper one would be a great option and that host can take 26650 cells.