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FrozenGate by Avery

NUBM44 6W+ 450nm Laser Diode

VisibleGreen said:
Maybe these diodes require an absolutely clean lens. Maybe typical residue on, well, anything will burn and damage the window? As if you have to treat it like opening up a harddrive. No dust whatsoever anywhere.
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Something I have noticed about all the N diodes from the A series on up is they have a hot spot in the center of the output. We have all seen how when focused to infinity that when burning wood/paper up close that its always the center of the box shaped output spot that burns first. Some diodes may have a higher center concentration of energy than others. It's possible that the duty cycle of these will have to be limited when being pushed hard. Now if the substrate can live without the can/window then great. Time will answer both these questions.
 





RedCowboy said:
Something I have noticed about all the N diodes from the A series on up is they have a hot spot in the center of the output. We have all seen how when focused to infinity that when burning wood/paper up close that its always the center of the box shaped output spot that burns first. Some diodes may have a higher center concentration of energy than others. It's possible that the duty cycle of these will have to be limited when being pushed hard. Now if the substrate can live without the can/window then great. Time will answer both these questions.
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And these aren't meant to be pushed as hard as we push them so there was no reason to use a better window. I think as long as you never remove the lens it should be ok without the can. It just makes it even more sensitive to build a pointer out of these now.
 
I don't mean to derail the thread, but I have to say the plpm4-450 package looks awesome.
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I'm not sure what you are talking about. What is this and can you provide a link to a discussion if one exists?
 
Something I have noticed about all the N diodes from the A series on up is they have a hot spot in the center of the output.
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That is actually the best part of the beam and corresponds more closely with the TEM00 mode. Multi mode diodes are able to lase on non axial more divergent paths because the gain is sufficient to allow this, but it is not optimal and so the power is less. The higher output of these diodes comes from the sum of many of these less ideal paths. Of course, the first failure point of the window will be at the highest intensity point.
 
planters said:
That is actually the best part of the beam and corresponds more closely with the TEM00 mode. Multi mode diodes are able to lase on non axial more divergent paths because the gain is sufficient to allow this, but it is not optimal and so the power is less. The higher output of these diodes comes from the sum of many of these less ideal paths. Of course, the first failure point of the window will be at the highest intensity point.
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Yes I like the hot spot in the center, but it may possibly be part of the window problem...if there is in fact a problem and not just a contamination issue.
 
maybe DTR can decan one of these diodes with the window problem and then turn it on to see if there is still something weird going on with the pattern.
 
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gif said:
maybe DTR can decan one of these diodes with the window problem and then turn it on to see if there is still something weird going on with the pattern.
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The emitter could be damaged when the window burned so if it is from a contamination of the window then it's just a matter of keeping it clean.
If it's from overheating then more heat sinking and shorter duty cycles. We all know how cheap TEC pads can be had on flebay. Fact is these are in commercial units expected to last 20,000 hours and I can tell you that these diodes are POWERHOUSES, even with a wider spot produced through the readily available 3 element lens the burning power is impressive. These have a lot of potential and require a lot of responsibility on part of the operator. Even a very large spot at distance was smoking dry leaves, the power is impressive.
 
I removed the can from a m140 with a cracked window. The diode only lasted a few hundred hours. Hard to say if I damaged it when I removed it. It was making spec power and the beam/ spot looked fine after removal.

Looks like the window may be the weak link on these new diodes?

In the host projector the burnt window may only reduce the output slightly and never be noticed.

Has anyone tested the current or optical power of these new diodes before they removed them from the projector?
 
logsquared said:
Looks like the window may be the weak link on these new diodes?
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I really don't think there is an issue with the window. I have gone through 11 blocks at this point most diodes paired with 4-5A drivers and so far only know of two people that had issues with burning stuff on the window. I see burnt contaminants on pretty much all diodes so it is not something new. I would find it hard to believe they would not have a window that was capable of passing 2-4X the rated power of the diode to be on the safe side.
 
I have gone through 11 blocks at this point most diodes paired with 4-5A drivers
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Wow! I didn't realize. I thought "we" were on the first or second block. That is good to know.

Is it possible to test the current or watts out before taking them out of the block. This way we have a benchmark of what the manufactures current spec is?
 
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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 would find it hard to believe they would not have a window that was capable of passing 2-4X the rated power of the diode to be on the safe side.
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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.
 
Something I know I am guilty of is not paying the upmost attention to is the spring except in the case of the 660nm long waveguide open can diodes.
If the spring is not put into a clean box with the lens when taken out of the module then it could pick up a fleck of anything on your worktable.
I use a larger spring that I put around the outside of the lens barrel on a lot of my open reds. This might be a good idea on these higher power diodes as well.
 
I may have just solved this mystery. It's been hot here all week, 95 temp during the day and we have had a lot of rain. Tonight it's raining, my ac is keeping the room a comfy 72 and I had my window open to watch the rain.
I shine a trusty old M-140 I have easily a 100 hours on at the tree line and notice the beam looks a little bit foggy in the wash around the spot, not bad just a little bit foggy. So I remove the lens to clean it with a micro fiber cloth. I did not look at the laser diode because I still had the batteries in and I never ever look down a loaded laser no matter what. I turn it on without the lens to look at the raw output and it's fxxked! I put the lens in and it is just a splattered mess. I take the lens and the batteries out, I look in and see the diode window has exploded. You can see a hole at the hot spot and a line to the left where a piece of the window is gone. It must have been the still hot glass being hit by cold moist air, that's the only explanation that adds up. Now I honestly can't remember if I had taken the lens out the day before I fired up the NUBM44 and discovered it was popped, but I do remember going down to my drill press to do something to the test jig it was in and I almost always take the lens out and put in an acrylic when I do that and I had been running it right before then, I'm sure I exposed it to cold moist air and that could have popped it without me knowing until I fired it up cold the next day. But it's user error in any case, we have to keep our diodes clean and dry. To be clear this is a M-140.

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It's a year later and I have half a dozen strong NUBM44's with no window problems and many hours of hard use, I must have contaminated these, I can see all kinds of junk even in these pics, thermal shock is something to think about, but it is user error in any event, we have to keep our diodes clean and dry and even more so as the power level goes up.
 

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Sorry but this is too funny, I mashed the can with needle nose and shook all the glass out of this poor old m-140 and it looks like hell but it's beaming away like a champ. p.s. Used laser for sale with custom modifications LOL
 

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