Diode lives AND lases at -100F?

hydrogenman15 · Aug 26, 2009

I got kind of bored and decided to make some "poor mans liquid nitrogen" and put the low powered diode from a PHR-803T sled in it (don't ask me why I would do such a thing). I powered it up and ran it at 38mA's and submersed it in the cryogenic fluid. To my amazement it function normally. So I just sat there and looked at it for like 10-15 minutes to see what would
happen... It just kept going like there was nothing wrong.:huh:
So I took it out and it still worked just fine. I'm not 100% sure how cold it was but it was certainly enough to keep a rubber band solid for a few seconds. YouTube - Poor man's "Liquid Nitrogen"

--Hydro15

Bionic-Badger · Aug 26, 2009

Well it's usually the heat that causes the laser to die or not function. I think those green lasers also need heat because the crystals need to warm up inside or something. Diode lasers are just semiconductors.

hydrogenman15 · Aug 26, 2009

Bionic-Badger said:
Well it's usually the heat that causes the laser to die or not function. I think those green lasers also need heat because the crystals need to warm up inside or something. Diode lasers are just semiconductors.

I've heard that laser diodes die simply because of the photons bouncing against the quantum well structure <-- I'm not sure I got that right but what i mean is that a laser diode is almost always destroyed by its own output. Your right about green lasers needing to be a little warm to achieve a good efficiency. I thought that the laser diodes die would most certainly brake off
by the temperature shrinking it. I also tried a ps3 and it seems to have survived as well...This is so strange.

I don't completely know how the Lambda shift works and at what point it will stop dropping a diodes wavelength?:can:

--Hydro15

jnrpop · Aug 26, 2009

At that temp you should start amping the current up, if you have a few PHR's to play around with, You might even find it stays constant and lives at 200ma, who knows?

hydrogenman15 · Aug 26, 2009

jnrpop said:
At that temp you should start amping the current up, if you have a few PHR's to play around with, You might even find it stays constant and lives at 200ma, who knows?

I doubt that the temperature is going to save it from its own output. From what Igort has told me it really isn't much about temperature or duty
cycles. He has tested a LOT of phr's and despite them being only 3 degrees above room temperature they still died in less then 20 hours of use 150mA's

--Hydro15

lasersbee · Aug 26, 2009

I guess there is one way to find out and be sure...
It's not like the PHR803T still costs $60.00..

Jerry

millirad · Aug 27, 2009

If you don't mind, we are all waiting to know. If it was me I wouldn't be able stop myself.

hydrogenman15 · Aug 27, 2009

lasersbee said:
I guess there is one way to find out and be sure...
It's not like the PHR803T still costs $60.00..

Jerry

Its not like its practical anyways.. IMO if you really want more power just get a better diode. The really reason I did this was to see just how low the wavelength would drop and the Lambda shift is definitely not linear. If it was you could do the math.

72F down to -100F =-113C temperature change and divide it by .3 and you get a wavelength drop of 33.9nm.

If it will contribute to the forum then I'll try it but if it dies I'm calling the "duty cycle monster" BS. I'll get some dry Ice in a few days and set up a DDL driver to ramp the current slowly up to 250mA's. I won't be able to take power measurements for obvious reasons.

--Hydro15

Benm · Aug 27, 2009

Its probably more rewarding to do this with red diodes than blurays. Due to the cold their wavelength will decrease, making the beam more visible instead of less visible (deeper into the uv) for blurays.

Laser diodes will work better at cryogenic temperatures, but there is still the possibility of COD, and thus to how much light you can produce without doing any damage.

Using dry ice with alcohol is a good way to chill things. I've used in the laboratory a couple of times... while not as cold as liquid nitrogen, it doesn't boil on contact surfaces and is able to freeze things much more quickly than dunking them in a dewar of LN2.

Downside of this is that this effect also works on fingers, and you have to be extremely careful not to get your fingers in there or even spill drops on your skin. As these alcohols are flammable, take precautions for that too!

hydrogenman15 · Aug 27, 2009

Benm said:
Its probably more rewarding to do this with red diodes than blurays. Due to the cold their wavelength will decrease, making the beam more visible instead of less visible (deeper into the uv) for blurays.

Laser diodes will work better at cryogenic temperatures, but there is still the possibility of COD, and thus to how much light you can produce without doing any damage.

Using dry ice with alcohol is a good way to chill things. I've used in the laboratory a couple of times... while not as cold as liquid nitrogen, it doesn't boil on contact surfaces and is able to freeze things much more quickly than dunking them in a dewar of LN2.

Downside of this is that this effect also works on fingers, and you have to be extremely careful not to get your fingers in there or even spill drops on your skin. As these alcohols are flammable, take precautions for that too!

Yeah, I think that the diodes gonna go COD too. don't worry I use goggles and gloves when I using this stuff.

Whats the best way to keep the diode insulated and still have good thermal conductivity?

--Hydro15

Benm · Aug 28, 2009

If you use ethanol and dry ice mixture, i suppose you can just dunk the whole thing in, alcohol isnt very conductive. It will become a bit of a thick liquid at those temperatures, somewhat like glycerine at room temperature.

As far as gloves go: Never use things like oven mits when handling cold ethanol... it will absorb into them and likely freeze your fingers dead before you can even remove them. You can use silicone-convered gloves that are water-tight, but i dont recommend using anything not specifcially made for this.

Ethanol/dry ice is far more dangerous than liquid nitrogen to work with - temperatures arent as low, but there is no layer of gas to protect you... dipping a finger in LN2 is a neat trick, but one which will cost you that finger with this stuff.

Hemlock_Mike · Aug 28, 2009

Dumb question here --- What is "poor man's LN2"? Why is it only -100 F ?? LN2 is far colder than that. Do you use a compressor with dry ice for a condenser?

Mike

hydrogenman15 · Aug 28, 2009

Hemlock_Mike said:
Dumb question here --- What is "poor man's LN2"? Why is it only -100 F ?? LN2 is far colder than that. Do you use a compressor with dry ice for a condenser?

Mike

The video explains it pretty well. Get some 99% rubbing alcohol and drop the dry Ice in it. Wait until the dry ice is bubbling slowly and the liquid should be close to the temperature of the dry ice. Like Benm said, this stuff is very dangerous. I also noticed that the liquid becomes carbonated, dropping a Mento in this stuff would be very dangerous...

BTW Benm, what gloves would you recommend specifically that I should get? Where? I have two diodes here, one open can and one PHR-803T. Which one should I try?

--Hydro15

Benm · Aug 29, 2009

I would go for the open can, as the result is more spectacular: even if you dont produce that much more photons, it will look a lot brighter due to the decrease in wavelength.

One thing i'm not sure about is if the diode will survive being immersed in ethanol or isopropanol, as both a potent solvents and could dissolve coatings and such. In that regard a closed-can red diode would be preferable.

For the gloves: I'd keep my fingers out of the mixture at all times, just lower the diode by its electric wires into the liquid - no need to touch anything. Brands like cryoguard or tempshield do sell 'waterproof' cryogenic gloves, but those are quite expensive ($100-$200), and still thick enough to hinder using your fingers on anything delicate (such as ajusting current).

I'd rather call it DIY cryogenics than poor mans LN2 - its probably in fact more expensive than LN2, but has the advantage that solid CO2 can be obtained more easily and can be stored for quite some time using very simple means (i.e. big thick styrofoam box).

millirad · Aug 30, 2009

^ Yep, I received a burn or 2 from LN2 that bubbled out of a dewar, while working in Semiconductor R & D at Intel Corp. We in engineering foolishly poured it across the floor towards "operators" who didn't know what we were dealing with. Btw, liquid Oxygen is much more hazardous. ;-/

Benm · Aug 30, 2009

Liquid oxygen is best avoided unless you know what you are doing and need it for that purpose - its never used for just cooling things. There is also something like liquid air, but its usually not sold in this form, but separated into nitrogen, oxygen and argon fractions each for their own application.

If anyone is considering using liquid nitrogen, be aware that it will codense oxygen from the air if left exposed, and you could potententially end up with mostly liquid oxygen after most of the mixture has evaporated.

There is no such risk using the CO2/alcohol approach, altough that mixture will draw water from the air, and could eventually freeze due to rising melting point with water concentration. It will obviously melt as the CO2 evaporates, so its no major concern.

Diode lives AND lases at -100F?

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