Cheap! 100mW/700mW 613nm (Orange) Laser Module

Hello Guys,

i have already posted inside the LaserPointer Forum. Many of you know it already, however i will try my luck here too.

I designed and build a prototype of a cheap 100mW/700mW 613nm Laser module. It is not a DPSS as you might expect.
Its using the diode thermal wavelength shift to drive a normal red laser diode down to 613nm. I already archived a wavelength of 616nm with a 700mW 638nm sharp Multimode diode.

The laser module can cool the diode really deep to shift the wavelength. I am currently getting -80°C but i am expecting -100°C by using a better tec.

Data:
The module is completely hermetically sealed and uses vacuum insulation. So no special equipment is needed to operate it. Just a normal Tec driver and a Laserdiode driver (a Live Lasersystems ColorDrive for example).

It uses around 60-70W for cooling and laserdiode.
Its quite small with a footprint of only 60x70mm and a hight of 40mm.

There are several options for laser diodes that could be used inside the cryo module:
633nm 100mW SM Ushio diode (around 180USD) -> this would give us the best (lowest) wavelength and beam, however its quite expensive (this would give us 613nm @100mW)
638nm 185mW SM diode (30USD?) -> this is quite cheap, has better power but worse wavelength, would be best for a cheap lumia
638nm 700mW MM diode (30USD?) -> cheap and the most power, worst beam and wavelength but the power may make some people consider it (around 620nm at 700mW)


I also have a comparison screenshot of the 616nm i already archived with a 700mW MM diode that was running at around 200mW. The other diode is a 660nm SM red.
Please dont look to closely at this janky setup, its my prototype. The module will not have the vacuum gauge attached to it in its final form. I also changed the mount for the output window and case lid.


I can get a price brake on the TEC used if i get enough people interested. I dont have a exact price for the complete module as i am currently investigating milling options for the case. I can say that in will be in the range of 500-1500USD depending on the configuration (diode used) and addons (drivers). A kit would be much cheaper but requires you to have a good vacuum pump and soldering skills. However the TEC would be 160USD (excluding shipping and customs) for one pice and 100USD for one if we can get 10.
SO if anyone would be interested in buying a kit or a complete unit, drop me a PM.

Best Regards
Stephan

Good to see you over here. How much for the best setup total? Ie best diode,driver tec. Etc…. Also I’d be interested to see if you can significantly shift green and blue diodes. Be interesting to shift out a 520 to 530/540. Be interesting to shift a 465 to 470/475 think that would be heating though. Still basically same setup.

660/638. 613. 575. 488. 525/543. 473. 445. Now that would be some Lumia. Or a mess but let’s you select sets of pallets colors. Like 660 613 575 543 445. Or. 638. 575. 525. 473. Or. 660. 613. 445. For a dark look etc….

be good for open can diodes too as you can dry Argon backfill

isthere room to add a second diode and pbs? Thinking of planters setup.

anyway price is king. Yes interested.

Hey Kecked,

unfortunately there is no space for a second diode. Even if there would be space, the tec would get overwhelmed with two diodes.
The two diodes wouldn't reach these low temperatures that are needed for orange.

However its easy to buy some dichroics (or PBS) and add a second module or diode to make a Lumia.
I am thinking about buying a cheap Chinese RGB module and changing the red diode to R660nm. This would give 660nm, 613nm, 520, 445nm. Thats already nice and still easy to add.
If i am feeling special i would add a 488nm and 405nm diode, this would give almost the whole spectrum: DeepRed, Orange, Green, Cyan, deepBlue and violett.

But i see your point, a lumia with just a DeepBlue (445), a deepRed(660) and a Orange would give a nice dark colorful look.

Argon Backfill is also not advisable, this would significantly reduce the cooling ability of the tec as argon would cary heat to the diode mount.
Thats why i am using a vacuum to keep the heat "away" or the cold "in" depending how you look at it.

For you green/cyan diodes: As i explained in the Laserpointer Forum, it would be much more advisable to cool diodes than heat them.
Cooling archives way more wavelength shift than heating.

Price is highly dependent on quantity. Thats why i am asking if anybody is even interested.
I currently have no better estimate as 500-1500€ I will update this as i get informations on my material and milling prices. That being said: my lowest estimate is quite optimistic and my highest quite pessimistic. I assume around 800€ but i can not (at this time) offer a concrete price.
However even my highest estimate is still worlds away from commercial Orange modules with this much power thus providing a very good value.

Hello Guys!

I now have a better estimate.

If we talk low cost, i can offer:
730€ with the 638nm 185mW SM diode, this module should reach 618nm. This would only be the module, without any driver.
If we talk the best module, ready to use, fully fledged we are at 1020€ including driver and the better 633nm 100mW laser diode. It should reach 613nm.
The module will use around 70W at 24V (around 3A).
Please keeping mind, every diode is different, so i cannot guarantee the actual wavelength.

If you want to get an even lower wavelength, we could stack a tec underneath the complete module. I didnt calculate a price and the power usage would be enormous (like >300W) and you could get to around 610nm.

Drop me a PM or leave a comment if you are interested. If enough people are interested, we could get the price down.

Quote:

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Originally Posted by Farbe

The laser module can cool the diode really deep to shift the wavelength. I am currently getting -80°C but i am expecting -100°C by using a better tec.

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Wow! You're getting the diode down to -80°C using just a TEC? That's impressive! How long does it take to cool down from ambient?

Quote:

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Originally Posted by kecked

Be interesting to shift out a 520 to 530/540.

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If you cooled a 520 nm diode, wouldn't that shift the output towards shorter wavelengths? So you'd end up at 490-500 nm or so.?.

I suppose you could HEAT the diode and shift it towards longer wavelengths, but I don't think the diode would survive the high temperature.

Eric (Planters) did some experiments years ago where he cooled red diodes using liquid nitrogen to get shorter wavelengths (so a little more than double the temperatures we're talking about here). I also remember that he had to insulate the hell out of the module to prevent condensation issues though.

Adam

-80°C is almost the maximum archivable. I have spend many hours researching and developing the case to have enough insulation for these temperatures. Insulation is everything with these temperatures.

Time to cool is not that long, around 2 minutes, maybe a little less. Thats because i optimized the thermal capacity of the diode mount.
This way the TEC does not need to cool much material. The holder is quite light, below 15g total including diode and optics.

Sadly 520nm or any blue/green/violet diode uses a different material that does not drift much with temperature. Only Red diodes show this property.

Heating is not really an option, we can not reach these high temperature deltas to have a good wavelength shift.

Planters reached much deeper temperatures and did not have a design constrain of using to much cooling power. So his setup was not good isolated, could not be, did not matter. I tried to make something thats actually usable inside a Projector/grating bank/lumia without having to use cryo liquids or high power. Therefor i had to sacrifice ultimate wavelength shift. However i still reached a good balance and got down to "low enough" for an nice orange.

Even if greens and blues drift less, if the single mode greens and blues I have even shift by +-3nm by the difference between heating and cooing them, it becomes useful for getting correlative Raman lines.

Interesting use for this technology, I would need to check the maximum drift that is reachable with blue/green/cyan.
What wavelength would you be most interested in? Maybe 405nm? I do have some diodes laying around and a prototype module for trying different diodes.
So if you want, I could try to "drift" a diode of your liking and see what's possible with solid-state without LN2.

really impressive and cool! My only concern would be the lifespan of the diode running at these harsh temperatures and when you cool at as much as you can a higher ambient temperature might give you some problems in terms of performance no?

Hello,

That should not be a problem at all. The lifetime drops by around half if you increase the temperature by 10°C. Allmost all laser diode degradation happens because of temperature related effects (electro migration / facet degradation).
So lowering the operation temperature while still using the same output power will increase the lifetime by quite a bit.
For lower temperatures, the diode gets more efficiency, so the current needs to be reduced to not have more output power than the facet can handle. Lower current means also slows electro migration = lower wear.
So we have two compounding effects that elongate the lifetime. Lower current at lower temperatures.


Increased ambient temperatures don't matter if you use a tec (like you normally would for diodes). I currently have this setup ready:

https://www.photonlexicon.com/forums...1&d=1634300040

Its running quite nice with a nice orange beam. (660nm and 532nm as a color reference beam)

That makes sense!
Thanks for clarifying!

With the mention of the liquid nitrogen video by tech ingredients, I looked and found it. He went down to 608 nm, but one heck of a lot of trouble to get there. Your unit to produce 613 nm is viable for both hobbyists as well as commercial sale, his, far too complex and large for most of us to want one. I like what you are doing and want one too, so from what I understand, that will be two of us so far.

To save those who might not have seen the Tech Ingredients YT video showing his large liquid nitrogen cooling setup some time to find it, here's the link: https://youtu.be/0w4czym1FFg

Perhaps this is basic stuff for you as a laser professional, but today I found this information regarding wavelength shifting of a NIR diode by as much as 10 nm just from the feedback produced when turning a grating in front of the diode inside an optical cavity, drawing below. Since feedback into the diode from the collimator and reflections forward of it can affect wavelength, this technique might be useful for your project too:

Attachment 58409

Perhaps by incorporating both the grating and TEC adjustments together you can reduce the wavelength even further? I just emailed the full article to you.

Want below -200 C?

Attachment 58439

Quote:

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Originally Posted by Laser57

With the mention of the liquid nitrogen video by tech ingredients, I looked and found it. He went down to 608 nm, but one heck of a lot of trouble to get there. Your unit to produce 613 nm is viable for both hobbyists as well as commercial sale, his, far too complex and large for most of us to want one. I like what you are doing and want one too, so from what I understand, that will be two of us so far.

To save those who might not have seen the Tech Ingredients YT video showing his large liquid nitrogen cooling setup some time to find it, here's the link: https://youtu.be/0w4czym1FFg

Perhaps this is basic stuff for you as a laser professional, but today I found this information regarding wavelength shifting of a NIR diode by as much as 10 nm just from the feedback produced when turning a grating in front of the diode inside an optical cavity, drawing below. Since feedback into the diode from the collimator and reflections forward of it can affect wavelength, this technique might be useful for your project too:

Attachment 58409

Perhaps by incorporating both the grating and TEC adjustments together you can reduce the wavelength even further? I just emailed the full article to you.

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Probably not.
I believe these gratings are used to narrow down the band from the available band you have.
This is to make a laser a more narrow band by throwing away the rest (Makes the peaks sharper).
I believe the grating is just becoming a wavelength selector so to speak for whatever is actually available within that laser.
Or at least that's what I remember.

I bet if that's the case though you will throw away a lot of your light.

Here's the article I was reading:

https://photos.imageevent.com/qdf_fi...20external.pdf - password: yellow

And now you pointed that out, the article is about LINEWIDTH, not reducing wavelength (edit: but the article ALSO mentions 10 nm wavelength shifting can be achieved).

I just received a communication regarding the Sterling Cryocooler I posted the link to, no way I can afford that device, far too expensive for hobby use, but it would have been awesome to see how far down we could shift the wavelength if chilling below -200 C.

Chris

Quote:

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Originally Posted by Laser57

Here's the article I was reading:

https://photos.imageevent.com/qdf_fi...20external.pdf - password: yellow

And now you pointed that out, the article is about LINEWIDTH, not reducing wavelength. I sure got off on the wrong foot. I just received a communication regarding the Sterling Cryocooler I posted the link to, no way I can afford that device, far too expensive for hobby use, but it would have been awesome to see how far down we could shift the wavelength if chilling below -200 C.

Chris

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Wouldn't be able to tell what but there are always surpluss products which may fit this need.. not great for wanting a steady supply to sell but for own use sure

I'm buying one of these units shown in the first post of the thread, but to build something myself I'm still looking for a chiller which will go lower than -100 C. with a five watt heat uptake, perhaps I will use a cascaded TEC module the same as Farbe is using in his design. However, I did find two more articles which demonstrate a grating can reduce linewidth as well as lower the wavelength of a laser diode by as much as 10 nm. So, now I have three sources of information confirming the wavelength can be reduced as much as 10 nm.

See the attached document.

"...Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to −64 ◦C, more than 85 ◦C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation is achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes."

Edit:

I have found another manufacturer of a Sterling Cryocooler which appears to be able to uplift far more than 5 watts of heat while keeping the temperature at or below -100 C. which are priced at $4200 USD for a sample piece. Although a quarter the price of the first company (ametek.com) I reached out to regarding their -200 C. (and lower) 5 watt uptake Sterling cryocooler, obviously still too high for a hobbyist, ouch.

Clearly, I'm not paying that kind of money for something I can do with a stack of TEC's, but to add the information I was able to find about the Twinbird cryocooler; the temperature of their cooler varies by heat load, as all of them do, but is able to uptake a lot more heat than the first device I checked on (although achieves -100 instead of -233). Here's a link to the $4200 USD unit: https://fpsc.twinbird.jp/products/detail.php?product_id=92

Blog on Sterling coolers: https://www.eevblog.com/forum/projects/ebay-stirling-cryocoolers

"I have a little experience with Sterling coolers in thermal cameras.

1. The fill of Helium is at around 200psi
2. The Helium fill leaks out over time, so reducing pressure and the ability to reach normal operating temperature (-196C)
3. You cannot tell a good sterling cooler from looking at it.
4. Untested Sterling coolers should be considered faulty and priced accordingly. A broken Stirling Cooler is an expensive paperweight.
5. A Sterling cooler that is described as working can mean many things. The motor runs, the cold end gets frost on it or more helpfully, the cold end reaches -xxxC. A Stirling cooler with low gas fill will still cool, just to not the normal operating temperature.
6. I have yet to come up with a safe way to refill a Sterling cooler. The fill port does not appear to contain a valve. It is a conical seat into which a threaded plug screws and indium is used as she sealing gasket. This needs a clever adapter to allow turning of the threaded plug whilst under 200psi of Helium pressure. I have all the required gauges and pipe work though.
7. Ballon Helium from BOC in the UK is pretty good but not ultra pure, as normally required for a Sterling Cooler. Any water content will freeze, causing piston issues. Ultra pure Helium may be ordered from BOC but costs around £150 in total and you are paying rental on the cylinder. The Cylinder is at around 250psi so a regulator can provide the required 200psi fill pressure for the cooler.
8. Air is being added to Helium tanks for ballon filling to protect the worlds reserves of this gas. A 20% air to 80% Helium mix is fine for balloons but will ruin the helium for Sterling Cooler use in my cameras.
9. Suicide by Helium gas hood is a well known method for those wishing to end their lives. For this reason, some suppliers are very suspicious about why you want pure helium as opposed to balloon helium. The 20% air in balloon Helium tends to make it non lethal.

I have two Sterling coolers that need a Helium refill. The OEM isn't interested and boding it and it would be very expensive anyway. If you buy an old Sterling Cooler, expect it to have lost most or all of its Helium fill. Helium molecules even get through the aluminium casing material of the cooler !"

Fraser

A Cryocooler is the way to go for lower temperatures. However quite expensive and with limited lifetime.

The grating can be used to tune the wavelength, its not only used to lower the line width. Its also used to lower the wavelength.

Tuningrange is not unlimited and depends on the gain bandwidth of the diode used. The 633nm diode that the paper and i use, can only be tuned by around 2-3nm at these temperatures.
The paper clearly states that. A grating does have losses and also costs a lot. So i did not consider it in my design.

I worked closely with my tec manufacturer and got around 115k delta T out of my tec.
Stacking more tecs does not make much sense. The seebeck effect does taper off with lower temperatures, so going to above 5 or 6 stages does not make much sense. Cryo cooler it is if you want below -100°C with any significant power.
So my design (except for the missing grating) is almost the lowest reachable without going to really expensive for the cooler or optics or diodes.

Thermal Design is also quite important at these temperatures. Having to much heat loss will have even the biggest tecs struggle.

Farbe,

Thank you for the update. I am also researching the available TEC's to determine which company offers suitable devices for this use, stepping through the same path you took in your research. I will probably just reach out for a consult from one of the reputable US based companies to see what they suggest. Edit: I have the info now, there are several companies, appears Laird is a good one.

I love the Sterling coolers, but not the price, even the less expensive ones are sky high priced for hobby use, so that isn't going to be something I will be using, unless I can find one at a good price on the surplus market. However, from what I'm finding on blogs, finding a used Sterling cooler with some life left in it is not something which can be counted on, as these devices have such limited runtime and have too many problems, unless you buy one for 20K USD, then those will last but the price is crazy for us.

Do you happen to know how far these diodes could potentially be shifted a lot more towards yellow if cooled to -200 C.? Just curious, too expensive for me to do so, but do you know if there is normally a limit to the ability to shift the wavelength, or if the shift is no longer as linear at the lower temperatures approaching -200 C? I will continue searching for this information, but if you knew that would save me some time, perhaps a lot. So far, I've found the shift on some red diodes can be upwards to as much as .3 nm per degree C. (typically between 0.15 and 0.25 nm/◦C), but so far finding no mention on what happens below -100 all of the way to -200 C.

Thank you for sharing the results of using the grating with this diode. 3 nm isn't much for the added complexity and cost, but I'm still interested, depending upon how much loss through the grating and added cost.

Above graph from an article showing the wavelength shift of a red laser diode through temperature tuning, with and without the grating. Article attached.

A Less Expensive Option: Multistage TECs

From: https://customthermoelectric.com/pro...tage-tecs.html

"Multistage (cascade) TECs can produce a larger Delta T than a single stage Standard TEC. Each additional stage adds greater capability in temperature difference (Delta T) but each successive stage adds less capability than the one before it. This leads to a limit of around 8 to 9 stages, but for most puposes 5 stages is the practical limit due to costs versus useful delta T increase.

The most common multi-stage peltier modules are 2 and 3 stage. A typical 2 stage TEC delta T capability can range between 80°C to 95°C. A 3 stage can reach 95°C to 110°C, a 4 stage can reach 110°C to 120°C, and a 5 stage can achieve around 120°C to 128°C. These limits do depend on temperatures, the specific multi stage TEC, the heat sink, and ambient conditions. Multi-stage thermoelectric modules often have much lower Qc_max capability compared to similarly sized single stage TECs. This is because increasing Delta T capability with multi-stage TE coolers decreases Qc capability. Each stage must move all the heat rejected from the stage above it and additionally lower temperature itself."

I just came back to add some more, I've been searching for a thermistor to measure the ultra low temperatures a multistage TEC can produce and not finding any, they don't usually go below -50 C, the lowest I've found so far at -58 C! However, a T-Type thermocouple will measure down to as much as -250 C. and the probes themselves are cheap, but the meters used with them, if accurate to -200 C. or lower, aren't so cheap. Just adding this here for others who might want to measure these ultra low temperatures too.

Another thing regarding these TEC's, the specified delta-T (or temperature difference between the plates) are specified without a heat load on them and usually (for multistage), the figure is only good in a vacuum, not in air or a gas.

Questions for the group:

1. I am still researching how the heat load affects the delta T and could use some help with understanding that, if anyone here might be able to help.

2. Does anyone know how much different levels of vacuum (i.e. 10 to the minus 3, 4 and 5 Torr) affect the full specified cooling performance of a four or five plate multistage TEC to be realized (assuming the spec. isn't too generous)?

Edit: Laird is telling me 10-6 Torr is ideal which is considered a hard vacuum. Investigating the cost of a pump which can pull down that far they are way too expensive for me, perhaps filling with argon gas instead could be a reasonable alternative over using xenon which although far better is very expensive to get in an easy to use gas canister.

I suppose there could be some kind of work around to inject the xenon gas from a glass ampule, which for a small chamber would be far less expensive, but due to the higher diode temperature the output would still be about 2 to 3 nm higher in wavelength than if using a vacuum, close to another nm more higher if using argon gas instead of xenon.

NOTE: I am making a lot of assumptions to throw these figures out like this without having any experinece in the matter, zero. So why am I filling up this page with this crap? I'm hoping someone might jump in here and show me better. I need to find what temperature can really be achieved with the available multistage TEC's when there is about 2 watts of waste heat from the diode. This could throw these figures way off if I am being too optimistic regarding how low we can get the diode temperature using a TEC, whether in a vacuum or not.

It is quickly becoming clear to me how much easier it is to just buy one of these from Farbie, as I am. Just the research on this is taking a lot of time, hours of googling over a period of days.

This graph shows the effect (to the delta T) of air, gas or vacuum upon both a single and multistage TEC:

Hey,

I will just chime in and help you understand the concept better:

As for the vacuum vs gas fill:
The gas inside the tec housing is just a normal heat conductor, just like iron would be. (however much worse of a conductor)
So sucking the gas out results in "less conductor" so in less heat conduction overall.
Choosing the gas depending on "heat conduction ability" e.g. thermal resistance will lessen the heat load because the gas will be a worse conductor of heat (thus less heat will "reach" the tecs surface).

The pressure of the gas is therefore directly related to the heat load. As well as chamber design. Imagine the iron example from before:
A 1" long iron bar would conduct heat quite fast. Heat one end with a blowtorch -> burn you fingers fast on the other end.
On the other hand, a 100" long iron bar could be heated with a blowtorch and leave you with cold fingers on the far end.

So this example shows: distance is also a factor in heat conduction.

There is also another problem that arrises, thinning the gas will actually increase the "mean free distance". This counters the "less conductor less heat transferred" part a bit. Have a google for mean free path length, much research to do.

All in all: there are multiple factors to calculating the heat load for a given pressure and a given gas. Its not as easy as: 1W for 1mbar and 0,5W for 0,1mbar or something like that.

I did many many hours of research to pull this off. Its easy to mount a diode to a tec, however getting LOW temperatures is quite a challenge and every little detail counts.

Thanks Farbe,

I just needed to find the heat conductivity of air at different pressures all the way down to a low enough vacuum. Instead of searching for information regarding thermalelectric coolers, I started searching for the heat conductivity of air in a vacuum and came up with this info:

Attachment 58457

I ran the above online converter at 10minus5 millibar which is considered a hard vacuum. The graph shows from .00001 up to a full bar, one atmospheric pressure.

From this, aside from radiant heat, I can see there will be very little conductivity of heat through the air if the vacuum is below 10^-4 Bar and lower (the line at near zero there and below). I needed this information to find an affordable vacuum pump which can pump the chamber down enough to have a multistage TEC operate at closer to the full delta T specification. Finding a vacuum pump which can pull down to just .0001 bar (10^-4) or .075 torr isn't cheap and they are big and heavy. Asking Laird, a TEC manufacturer, if they had a multistage unit which could produce -100 C. with a 2.5 watt load in a hard vacuum and they said no, the closest they had would chill to -60 C.

Yes that seams about right.

Now you just need to optimize the other forms of heat transfer.

That is where experience is golden. I have none, but hope to. I will have the one you are building for me before I get anywhere close to building my own attempt at it.

I was trying to understand why a Xenon fill would have better performance than Argon... Then I looked up the thermal conductivity and was very surprised to see that Xenon has the lowest thermal conductivity when compared to over 30 common gasses. (Link) Also, unlike some of the other gasses on the list, Xenon is the clear winner across all temperature ranges. Other gasses switch their positions in the ranking depending on the temperature. Huh! Who would have thought?

But yeah, at 200 Kelvin, Xenon's thermal conductivity is 5 times lower than air, and 3 times lower than Argon. So for optimal results, fill / purge the cavity with Xenon first, then seal it up and pull the strongest vacuum you can. That way whatever gas is left in the chamber (however rarified) will have the lowest possible thermal conductivity.

Agree that finding an affordable vacuum pump is going to be a bitch though.

Adam

That's a great idea to fill with xenon and then evacuate, I suppose filling with argon first would also be better than just evaucuating air, if using a pump which can't get down to a 10minus6 or 5 level, thank you for suggesting. I've been looking at the available vacuum pumps on ebay, but with the unknown condition for most of them, and the high shipping cost to me in Qatar, I will look for something locally first. If new, then I don't need to worry about whether they are just heavy pieces of iron I can't use for anything else. However, I expect anything I will find here will be Chinese junk. I would be happy with a .075 torr vacuum, especially if filled with argon or xenon first, but finding a canister of xenon is another issue for me here.

Quote:

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Originally Posted by Laser57

high shipping cost to me in Qatar

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Ouch. Yeah, that's going to complicate matters.

Quote:

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but finding a canister of xenon is another issue for me here.

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Plus Zenon isn't exactly cheap, even in the USA.

Adam

Yes, getting things shipped to Qatar isn't difficult, but Fedex isn't cheap either.

Communicating with Laird about their TEC's, they don't make one with the substrate doping needed to efficiently cool a 2 watt heat load on a four to five layer TEC at temperatures below -50 C., does anyone know which TEC manufacturer does? They didn't offer that info to me.

It's a materials problem when trying to reach from -80 to -100, their TEC's can't handle that much heat load and reach that far down at the same time. I could run the diode at lower power.

Edit: I'm thinking to solve this to go big and use brute force, having a multistage TEC which starts out with a TEC which is much larger at the bottom and thus the top TEC will be proportionally larger too. However, I am sure that induces other problems; higher radiant heat and just more heat in the whole cascade all together, so not sure that will work. Even if I can't get to -80 C. and some other temperature colder, that's fine, I don't give a damn about efficiency except for the extra heat the entire assembly will generate. I'm betting one could spend a career chasing this rabbit. Of course, I could just give up on a thermal electric cooler solution alone and perhaps use a TEC along with a bottle of freeze spray too to bring the temperature down further, but this is another area of research for me, how far can that bring it down? I'm finding that Chemtronics Freeze Spray can bring the temperature down to -51 C. Perhaps anything short of liquid nitrogen won't help enough.

More research to follow, I will report back later if I find something in a can which can produce colder evaporative temperatures. Perhaps hitting the diode with -50 freeze spray (conductively coupled to it, not directly on it) will allow the TEC to reach much colder temperatures at a minimum of solvent use making it economical. I'm hoping most of 2 watts could be taken away using the spray allowing the TEC to reach near loadless temperatures.

Edit again: Adding more.

Dry ice is -78.5 C. I imagine CO2 sprayed on something will be colder than the -50 C. produced by chemical freeze spray, still researching...

Thermal conductivity of gasses: https://www.engineersedge.com/heat_t...vity-gases.htm

Photo of my own chiller project parts (Farbe is building one for me too, which will be finished first). Of course, as evidenced in this photo I have a long way to go, including a vacuum pump (if I decide to buy one, $$$) which may be over a year from now before I am ready to begin the build. I'm a slow builder, that's why I'm buying one. I was able to buy this heatsink from a Melles Griot DPSS laser from a forum member here, perfect for this!

This TEC6 is probably jumbo oversized for what Farbe uses and likely not doped for the uber low temperatures possible inside a vacuum, but I want to give it a try. If I could find a TEC with the low temp. doping I'd buy it, but so far I haven't found one anywhere, just know it is possible. Base layer is 62 x 62 mm, top 20 x 20 mm.

Attachment 58490 Attachment 58492Attachment 58491

Due to the expense of a high vacuum pump, I might fill the chill chamber with Xenon gas instead of a evacuating.

Quote:

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Originally Posted by Laser57

Photo of my own chiller project parts (Farbe is building one for me too, which will be finished first). Of course, as evidenced in this photo I have a long way to go, including a vacuum pump (if I decide to buy one, $$$) which may be over a year from now before I am ready to begin the build. I'm a slow builder, that's why I'm buying one. I was able to buy this heatsink from a Melles Griot DPSS laser from a forum member here, perfect for this!

This TEC6 is probably jumbo oversized for what Farbe uses and likely not doped for the uber low temperatures possible inside a vacuum, but I want to give it a try. If I could find a TEC with the low temp. doping I'd buy it, but so far I haven't found one anywhere, just know it is possible. Base layer is 62 x 62 mm, top 20 x 20 mm.

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Due to the expense of a high vacuum pump, I might fill the chill chamber with Xenon gas instead of a evacuating.

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while not perfect, a hand pump used to bleed brakes is cheap and gives a pretty good vacuum. For this use I bet it’s fine.
Xenon is ridiculously expensive. You also don’t need to cool a large area. You could make the enclosure follow the slope of the tec so the vaccuum volume is very small. Harder to make much save a lot on xenon.

Kecked, I need to ask Farbe how much the vacuum pressure affects the stacked TEC performance, i.e. if .01, .001, .0001 and .00001 Bars. I expect he can give me some idea.

At this point, I think I've highjacked the thread. I better make my own on this project. This thread is meant to see who might want to buy these units as a group to make them less expensive.

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Received the 613 nm laser today, after many months stuck in US customs, but it arrived!

Now working on 607 nm: https://www.laserdiscourse.org/t/nik...project/261/36

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444 nm pumped Pr:YLF

200 mw? Nope, guess again :) Hopeful to produce several hundred mw orange power. This is a group effort of several forum members.

This is so cool! Eagerly waiting to see what your group is able to achieve!

This project is too expensive, I'm nutz for spending what I have already just for the crystals and 444 nm laser diodes alone, the OC's are not cheap either but I'm ordering extras, so that is part of why I'm spending too much. Maybe after the new year we can report something.

Received the custom OC's today for 607 nm.


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https://youtu.be/EULhaq7L4Ss

I can't wait to see your results!

Excellent work,
I'll have a full read of the thread this evening, but here's an old old vid I made many years ago if that's of any use:
https://www.youtube.com/watch?v=ygIn...l=DanielBriggs


All the best,
Dan