New Video. How low can you go?

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Originally Posted by planters

FutureDesign,
Look @ post #39. I am now using an all aluminum set up with substantially shorter and thicker thermal paths and my estimate is 2-3 C temperature drop from the diode flange to the LN2. The entire assembly will be held in a cryostat. Two diodes will then be externally PBS-ed,spatially filtered and fiber fed to a projector. The problem with submersion is that without pumped and flowing LN2, the concentrated heat source will likely lead to bubbles. These can be erosive as well an obvious optical nightmare (unless you are looking at a lumia right out of the box).

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Sorry, I missed the #39 post. Just purely amazing that the 500mW diode could be pushed to 5 times the rated output. However, not very practical :-)
I don't understand what you mean by bubbles leading to lumia effects. Are you referring to my idea with the submersed fiber coupled diode? Exactly where would the lumia effect be introduced? Maybe I was not clear, but I meant submersing a sealed fiber coupled diode and just have wires and fiber exiting the tank. No direct light through the liquid.

I can't wait to see your setup with 2 beams and the PBS. Wonder what will vapor most LN2? The heat from outside or the energy from the diodes...

Btw. leave the red already and get going with the 445's :-D

Best regards
Jan Thogersen

Pushing a fiber coupled diode to LN2 might lead to some interesting issues at the fiber to metal hermetic seal.


Eric, your box with the Cryocooler is at the shipper, I dropped it off before I left. However, I need you to resend your shipping address, Ohionet dumped my inbox contents. CC runs off 24V VDC at a LOT of amps. Once I have the address I can call her from BZN and get it shipped.

Mophead, if your reading this, I need your address too... Same deal. Server disk auto-cleanup.

Steve

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Originally Posted by mixedgas

Pushing a fiber coupled diode to LN2 might lead to some interesting issues at the fiber to metal hermetic seal.
Steve

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Fiber to metal? Where would that be? Anyway, I get the point and think that you are right. A "flexible" epoxy seal would be like stone at LN2 temperatures. The thermal expansion of the various materials would probably be the show stopper for that idea.

Jan

Steve,

I'll PM the address and did you remember the golden treasure map?

FutureDesign,

You're right, no luminia if the LN2 cannot access the fiber/diode interface. However, I still am not excited about this approach because I do not know if this particular diode is available fiber coupled in order to test this out and I would not want to tackle the coupling and sealing of these components. The thermal transfer through my more "conventional" set up should be really good and avoids the possibility that the concentrated thermal load at the diode in static LN2 will lead to the boiling and reduced thermal transfer because of the gas interface. My estimates are a LN2 hold time of 24 hours and a full up run time of 4-5hours per fill. The glass transition temps of most plastics are an issue. That is what makes this a little more challenging and more fun.

The reason I am moving ahead with a practical orange module is that the the 445nm diode is expected to temperature shift much less. The published delta for GaN is approx 0.05nm/degree and this is to even shorter wavelengths than 445. As far as power is concerned, I am interested in finding out how high the 9mm diodes could actually go. I have the diodes and the mounts. If crazy power in the +6W range is possible then a similar module producing 12W with a dual diode, PBS-ed in a beam the size and divergence of an expanded single diode would defiantly be worth doing.

I just posted a new video that looks at the effect of cooling on the 9mm 445nm diodes. As I had suspected, these show less impressive improvement than the AlGaAs Red diodes with cooling. And, if I was planning a blue laser installation, I would at most try to keep them at or a little below room temperature. This is where the benefit, although small, comes cheaply and could be conveniently achieved with a TEC.

Hope you enjoy it.

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http://www.youtube.com/watch?v=v9HH-z6jl2g

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Thanks for this interesting video!

Any idea why once I go lower that 45 degrees I start to lose power? I am guessing the optics are fogging up some, but curious if there are any other thoughts.

Do you mean lower than + 45 C? If you mean lower than - 45C then, yes the optics could be fogging and this is first seen as a power loss and later a deterioration of beam quality. But, the "later" almost always happens if you wait for it and so if you fail to see any beam deterioration after several minutes of operation then this is probably not it. The V. drop across the diode increases as temperature drops and at least with the flex mod drivers can even lead to a "LED- insufficient funds" warning.

Sorry about that, it is happening at a positive Fahrenheit. Should have mentioned the units measured. Ill have to check vdrop as it does operate very close to the edge. 12v supply with 4 diodes in series. I was thinking it was a vdrop of 2.5-.7 across each. Ill swap a 15v supply in and try.

Thanks.

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Originally Posted by planters

Do you mean lower than + 45 C? If you mean lower than - 45C then, yes the optics could be fogging and this is first seen as a power loss and later a deterioration of beam quality. But, the "later" almost always happens if you wait for it and so if you fail to see any beam deterioration after several minutes of operation then this is probably not it. The V. drop across the diode increases as temperature drops and at least with the flex mod drivers can even lead to a "LED- insufficient funds" warning.

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WOW! Amazing video, Keep it up!!!!

I need further more video that will help me out.........