Can anyone help identify the purpose of this 782nm laser diode?

[CurtisOliver]

It seems that it is possible for the laser of which it pumps to have a CW output according to a couple of references. There was reference in one article to the pump diode being QCW. The CW thulium was pumped by a 80W 782nm. So it seeming likely that the diode you have could be CW. These laser may be Q-switched for the medical applications? :thinking:

 

[Alaskan]

That's a lot of power then I like that. These were made so long ago hard to find info, Coherent here I come.

 

[CurtisOliver]

If they are QCW/CW then yes, that is a lot of power. It is hard to find much on 782nm in general, let alone the diode that you want to get.

Edit: Just found this. All I keep coming across is 60/80W diode stacks, yours are 120W and do seem to be CW.
https://www.researchgate.net/publication/258721915_Volume_Bragg_Grating_temperature_gradient_effect_on_laser_diode_array_and_stack_spectra_narrowing Click download full-text PDF.

You need to find out the operating voltage but they seem very similar to 808nm diodes. 2.2v per stack @ 75A? An 80W stack appears to have 6 diodes. If each is 2.2V then 13.2V is required. If we follow the same rule of thumb you can estimate that the 120W have around 9 diodes. 9 x 2.2V is 19.8V. 120W @ 19.8V/75A?
Let me know how far off I was when you get a reply from the manufacturer.

 

[Alaskan]

Thanks, yes, that finding is great. Lemme see who I can reach at Coherent tomorrow. BTW: Here's a atmospheric transmittance graph for a range of near-IR.

ET can call home at 780 nm, for that matter low atmospheric attenuation at 808nm and 1064nm too. Each in the wavelength ranges we can find fairly high power surplus lasers.

Regarding the voltage, I had assumed they were all fed ~2.2 DC voltage in parallel, maybe not, but all of my 40-50W 808nm diode arrays are built that way.

 

[CurtisOliver]

You're welcome. It was a mission to find anything particularly useful to be honest. I hope Coherent reply and fill in the missing pieces of information.
780nm is by far the best wavelength to use for that.
If later on in my lifetime we get ET contact, then it will all be down to you. :bowdown::thanks:

 

[Alaskan]

I need pulse for high peak power, but then the average power is crap.... I have YAG's for high peak power, diode arrays for CW or QCW, but nothing long pulse between the two. The advantage of 782nm is an inexpensive camera can be used to see the beam, 808nm too, but at 1064, the cameras I can afford are not very sensitive there.

I can do SHG with 1064nm for high peak visible power, but then airplanes are a problem. Better I stay at IR for my experiments and only use vis laser light indoors with goggles on. Must be very careful with IR too, for that matter, but at least I won't be flash blinding anyone at a great distance. Although it's all about power density in each case. To expand, or not expand the beam, is the question. Expanding the beam and you can deliver more power density at a distance, but then if expanded enough, far less a hazard. That's why I am collecting large PCX lenses, up to 14 inches diameter for my biggest one. Most are 3, 4, 6 and up to 10 inch diameter for my experiments.

 

[CurtisOliver]

You may be able to pulse these still, but I can't say with any certainty. Different papers gave different testing conditions. You need Diachi to pop by, he's good with pulsed lasers.
I reached the limit of how much I can find for you. Nothing else on that diode whatsoever.

Edit: I thought the diodes were run in series, that is why you can get diode power supplies 10V 70A for up to 5 diodes.

 

[Alaskan]

All of my high power 808nm FAP arrays are 2 volt, a bit higher up to 2.2 for some. The bars they use are all fed DC in parallel.

 

[CurtisOliver]

Ok, so the stacks are parallel. I was getting confused with multiple diodes rather than stacks. Well in that case who are probably looking at similar specs, 2.2V @ 75A.

 

[Alaskan]

At roughly 45-50% efficiency, 2 VDC X 75 amps could produce the 120 watt output rating. Edit: Either the voltage or efficiency, or both, must be less for 120 watts out if rated for that power at 75A.

 

[CurtisOliver]

After doing the calculations I can see that something isn't quite right. 2V x 75A = 150W. 150/80%=120W. At that rating the laser would have to have a electrical to optical efficiency of 80%. At 2.2V x 75A the laser would have an efficiency of ~73%.
2.2V x 65A is what my 50W 808 needs. 2.2V x 65A = 143W. That is roughly 35% efficient which sounds about right. For 120W we would need ~343W. 343W/75A=4.57V.

 

[Alaskan]

Voltage must be different, or efficiency much lower than I think.

 

[CurtisOliver]

Yes, it is both. The efficiency is around 35% and voltage must be much higher.

 

[Alaskan]

That tracks, I remembered the efficiency of my FAP800 high power laser modules incorrectly, only 35%. 2 to 2.2 VDC, depending upon the module power output rating.

 

[CurtisOliver]

Yep. It is possible that 782's could be more efficient as not much is know about them, but we should presume the opposite. Lets say 25-30% as 808 is pretty well developed. This could put the voltage anywhere in between 5-7V. This is why you need to find this out from Coherent. It is all guess work from now on.

 

[Alaskan]

Here's a somewhat similar Coherent product, except for 808nm:

Web page: https://www.coherent.com/lasers/laser/diode-lasers/horizontal-diode-laser-arrays

Two-bar through five-bar horizontal linear arrays designed specifically to provide the highest reliability and lifetime in high-cavity-power, side- pumping applications. Coherent’s industry-leading, front-end technology, including our unique AAA material systems, combine with rugged PulseLife technology to produce reliability of >20k hours for most products. CW diode laser arrays employ electrically-isolated macro-channels, enabling tap-water cooling.

QCW arrays are conduction-cooled and require no water cooling. Standard horizontal arrays are available at 808 nm, in 2-bar through 5-bar configurations. Custom configurations and additional wavelengths are available on a case by case basis.

Data sheet: https://cohrcdn.azureedge.net/assets/pdf/PulseLife-CW-Horizontal-Array-Data-Sheet.pdf