New Video. How low can you go?

[planters]

Would be a cool idea. Build a projector that has modules in it with containers to put dry ice in it so you have 2 watt of red just for the show :-)

Edison, we think alike! My target at this point is to test the 9mm 445nm diodes in the same way as the P73. Then to determine if this just gets better @ -193C or is a FAIL. Whichever way this goes, either -80C or -193C; build a better version of the test chamber (although the general lay out is pretty elegant ) and mount 4 of each diode type in a common cold compartment projecting out through 1 or 2 larger windows. All the beam manipulation, including knife edging, is done outside and @ RT. Both LN2 and dry ice are inexpensive, widely available and who could resist the allure of a cryogenic laser releasing wisps of smoke during a show. It is like a built in fogger.

[swamidog]

Edison, we think alike! My target at this point is to test the 9mm 445nm diodes in the same way as the P73. Then to determine if this just gets better @ -193C or is a FAIL. Whichever way this goes, either -80C or -193C; build a better version of the test chamber (although the general lay out is pretty elegant ) and mount 4 of each diode type in a common cold compartment projecting out through 1 or 2 larger windows. All the beam manipulation, including knife edging, is done outside and @ RT. Both LN2 and dry ice are inexpensive, widely available and who could resist the allure of a cryogenic laser releasing wisps of smoke during a show. It is like a built in fogger.

[edison]

Nice cool idea. A laserprojector with build in fogger and have damn bright beams. I wouldn,t go higher then a 1 watt p73 setup and who know you can have a beam with 4 watt or even more in red. The blue could be maybe a 3 watt setup doiing 6.

[krazer]

I would be interested to see how long the diodes last with that kind of abuse! I suppose as long as the facets can take it (which they should be able to do no problem if the 2+w 445nm diodes with a smaller active region are anything to compare to) it shouldn't be any worse than similar (input) powers at room temperature.

Do you have a way to measure the wavelength shift? I would imagine that they are starting to get quite orange at -80C and by the time you go to LN2 conceivably they could start to approach what some would call yellow (or at least amber)

[planters]

Do you have a way to measure the wavelength shift? I would imagine that they are starting to get quite orange at -80C and by the time you go to LN2 conceivably they could start to approach what some would call yellow (or at least amber)

Although I don't have a wavelength meter, the monochromator is pretty good. When calibrated to HeNe @ 633 the walk off down to my other HeNe @ 543 and Hg @436 is no more than 1-2nm. The peak drop of 13 nm @ -80C and 400mW decreases as the current increases and the junction warms. At 1.9 W the delta is 7nm. The published shift of the AlGaAs diodes is 0.25nm/C and so I suspect the junction is running about -28C below RT despite the high current.

I would be interested to see how long the diodes last with that kind of abuse! I suppose as long as the facets can take it (which they should be able to do no problem if the 2+w 445nm diodes with a smaller active region are anything to compare to) it shouldn't be any worse than similar (input) powers at room temperature.

Also, the IR diodes @808nm generate 8W from a similar area and @ RT.

[Vidal Wolf]

Great work. Get a spectrometer to check the mode hops and frequency changes as its cooling down. Also, purge the diode chamber with dry nitrogen or co2 so condensation and frost wont become an issue on the output window.

[planters]

Great work. Get a spectrometer to check the mode hops and frequency changes as its cooling down. Also, purge the diode chamber with dry nitrogen or co2 so condensation and frost wont become an issue on the output window.

I will look @ a spectrometer and see what might be available from E Bay. And thanks for the offer, I might just take you up on that. The purge will probably not be necessary. As long as the chamber is hermetically sealed and I mean rigorously then the fixed water content within will accumulate on the cold plate which, as the coldest surface available, acts as a getter for the moisture. I learned this nice fact when working with CCD imaging cameras that operate down between -100 and -200C within a sealed, but not an evacuated chamber. Most of the window condensation occurs on the outside surface from the the room moisture as the window cools and that's why I took the precaution to actively heat this window.

[Soulstorm]

Loved the setup and video, planters. The overclocker in me especially appreciated it. Thank you for sharing.
Wish there was a way to measure junction temperature. Would a non contact thermometer be of any use to get a little closer?
Would love to see some LN2 on this rig

Have been investigating something along this line too, but less extreme. Few months off before the trigger could be pulled on the build though.

[planters]

Wish there was a way to measure junction temperature.

I think the spectral shift is pretty good and direct. I have tested another AlGaAs diode (the LOC series) and as long as the drive current is kept low, the shift follows the bulk (mount) temperature fairly close to the 0.25nm/C rule.

[Soulstorm]

the 0.25nm/C rule.

When I first watched your video, I was horrified that rule was seemingly not in operation, forgot about all the extra juice you fed it!

Did find your comments about the DARPA project to be rather interesting. The very best publicly available single wavelength leds are over the 50% mark now, with lasers not far behind. Not to mention the best phosphor conversion LEDs for last year or so are using 60%+ efficient sources, after stokes and optical losses. Funnily enough the top company producing them has had large amounts of funding by DARPA. Very interesting times ahead.