Very Strange Beam Distortion?

[crashmidget]

Hi Everyone,

I recently bought several NUBM44 diodes and some lenses etc. from DTR and so far I have 2 NUBM44's built and running. Both are running at
4.5a with G8 lenses but I don't have an LPM so I can't give specs on the wattage, but assume they are at least 7w. One I use for testing optics and
am constantly changing lenses. I assume this one will be toast sooner than later. The other one, the one this post is about I set up to be long lasting.
G8 lens set to infinity and focus or lens changes done through beam expanders and or other external lenses, I rarely if ever expose the diode. The
other day I had to remove the G8 so I figured a quick check of the raw beam profile and a cleaning were in order. When I turned it on without any lens
I saw the strangest artifact. It doesn't appear at all with a lens so I never noticed it before. I immediately checked the diode window and it took quite
some time and intense magnification to verify a small discoloration on the diode window. I assume it's burned but it's very difficult to see. I can't take a picture
of it, haven't figured out how to get a photo that magnified yet. But here is the beam profile. The extra bright line, perfectly vertical and dead center is what is
concerning me. Has anyone seen this before? Do I need to de-can this diode? I will if I have to but would rather not to protect the diode. Any thoughts or advice will be very much appreciated. Thanks - Crash

 

[steve001]

Hi Everyone,

I recently bought several NUBM44 diodes and some lenses etc. from DTR and so far I have 2 NUBM44's built and running. Both are running at
4.5a with G8 lenses but I don't have an LPM so I can't give specs on the wattage, but assume they are at least 7w. One I use for testing optics and
am constantly changing lenses. I assume this one will be toast sooner than later. The other one, the one this post is about I set up to be long lasting.
G8 lens set to infinity and focus or lens changes done through beam expanders and or other external lenses, I rarely if ever expose the diode. The
other day I had to remove the G8 so I figured a quick check of the raw beam profile and a cleaning were in order. When I turned it on without any lens
I saw the strangest artifact. It doesn't appear at all with a lens so I never noticed it before. I immediately checked the diode window and it took quite
some time and intense magnification to verify a small discoloration on the diode window. I assume it's burned but it's very difficult to see. I can't take a picture
of it, haven't figured out how to get a photo that magnified yet. But here is the beam profile. The extra bright line, perfectly vertical and dead center is what is
concerning me. Has anyone seen this before? Do I need to de-can this diode? I will if I have to but would rather not to protect the diode. Any thoughts or advice will be very much appreciated. Thanks - CrashView attachment 65633

Since you saw something on the window what's the mystery?

 

[crashmidget]

The brightest part of the beam is where the distortion is, and the symmetry of the distortion both vertically and positionally (dead center) has me concerned that something else is going on? My concern is whether or not I need to de-can this diode to keep it
from sustaining any damage from the anomaly.

 

[Alaskan]

If the window has a problem in it where most of the energy passes through, it will probably get worse. Your decision, of course, but unless that bothers you, I would leave the can on. If it didn't have that problem to begin with, I expect the problem will progress requiring a de-canning.

 

[crashmidget]

I decided to leave the can on. Last night I was using it and the beam went way out of focus. I checked the window and sure enough
it was toasted. I went ahead and de-caned it. I'm pretty careful when de-canning, I use a micro vacuum to keep debris away from the
diode and I have a very sharp set of micro-files that I use. I put it all back together and everything went off without a hitch. When I fired it
up however, without the lens, the dot was not a bright rectangle but a dim circle. With the lens, it still burns but it's way down on power?
No idea why? Any suggestions?

 

[Alaskan]

Maybe a reflection damaged the diode facet? I had something similar happen with the window on one of my NUBM44 diodes, I am not sure the windows are designed to take the power we over drive them to.

 

[Encap]

replace the diode with a new one --would restore the laser builds output power and be a good check of the driver eliminating any concern that it is part of the cause of low output

 

[crashmidget]

Definitely going to replace the diode. I've got a few on hand but no NUBM44's. I could use a NUBM06... not sure yet. But I agree
with Alaskan. I've had a couple of these burn the window despite taking every precaution against contaminants. I only use 90+ percent alcohol and always one swab one wipe. It could also be the optics. I've had 3, one still up and running strong. All have G8 lenses and I try not
to remove them. I do have quite a collection of optical elements and and am always experimenting with making beam expanders etc. Might be getting a reflection but it's impossible to tell. $80 for a diode isn't cheap, but it's not the end of the world. Maybe the way to go is to set the drivers a bit lower (3.5a -4a) instead of 4.5a for builds I intend to play with optics on, and keep a couple of 4.5a builds set up in a permanent
configuration. If the 4.5a builds continue to have the same problem, we'll know Alaskan is right..

 

[paul1598419]

Decanning these blue diodes has always led to premature failures. If you need a diode to test optics with, the NUBM44 is likely your worst choice. I think I would use a a solid state laser as the beam profile is MUCH better, but any other far less divergent beam diode will likely do.

 

[crashmidget]

Paul1598419 you couldn't be more correct...but I've got a serious problem. I'm addicted to the power...I NEED the power~!