Testing hi power laser diode arrays.

I need a quick & easy method for testing a 40W 808nm laser diode array, that doesn't require a full power supply. Can I do this with the diode test function on my DMM, if I observe proper ESD protocols? The reason for this is that I just bought a 40W Dilas laser diode array from eBay, & it comes with a 30 day guarantee. The LD is supposed to be new, but I didn't see any type of shorting clip on it in the listing picture. Naturally, this has me a bit worried, & I don't think I can build the power supply, cooling, etc within this time frame.
Ideas, anyone?:thanks:

I just got a 12 watt 808 (FAP800) and I'm going to start with a computer supply having 3.3 volts at ~25 amps as one of the outputs. I'm working on current control ideas here but there tons of old computer supplys floating toward the dump out there.

HMike

I was thinking along similar lines myself, except that I need a power supply capable of >50A output. I strongly suggest that you use some form of active current limiting with your diode, because the acceptable range of voltage to any laser diode is quite small & hooking it directly to 3.3V will likely destroy it. There are some simple current regulator circuits available online, & these could be adapted to your laser diode use simply by using higher current transistors. Mine is a bit more difficult, as there aren't many transistors with 50A collector current capabilities. I'm also considering building a conventional line operated power supply, based on a reworked microwave oven transformer, with an active current regulator.

The amount of R&D & building that I have to do is why I need some method of testing my diode before the guarantee runs out.


BTW: Try to find the datasheet for your diode before you go much further. One thing that surprised me when I looked thru the DS for my diode is the narrow operating temperature range...20-30°C, with 20° for maximum output. This bit of info caused me to revise my plans from simple heatsinking to TEC cooling.

One of the bolts on the diode itself is there for shorting purposes (ESD) You have to remove that bolt in order to test it. I would not recommend using the diode function on your DMM to test the diode as it could potentially blow the diode. I blew my 40W before I had a chance to play with it. I can't honestly think of a way of testing it other than sending it to someone who does have a psu necessary to test it. (I'd be happy to do so)

Thanks for that information, you probably just saved me a diode. The situation with this diode has changed a bit; I am no longer under a time limit. When I received the diode, it was obviously not new, & was missing the shorting clip. It was listed on eBay as unused. Worse, the factory package had "overvoltage ~8V" hand written on it.:wtf: I contacted the eBay seller & they immediately issued a full refund & let me keep the diode to boot! I used the refund to buy a pair of used, but tested, 20W diodes, which are on the way now.
I guess I have to build that supply now.
What do you use to run your hi-power diodes? This is my first step into the world of hi-power LD arrays, although I have plenty of experience with single emitter diodes & gas lasers. I have a home built 20W CO2 laser, set up for cutting, on the bench now. This is the most powerful laser presently in my collection.

Thanks for the test offer, but I am in Canada & cannot afford shipping costs at the present time.


BTW: If anyone has a circuit for a 50A or better current regulator, I could really use it.:beer:

IIRC, you can use Vicor DC-DC converters to drive high current laser diodes. There are a few treads about this over on PL, definately worth a read if you're interested.

digital_blue said:

IIRC, you can use Vicor DC-DC converters can be used to drive high current laser diodes. There are a few treads about this over on PL, definately worth a read if you're interested.

Click to expand...

I'm interested, but what is PL?

PL (Photonlexicon) is another Laser Forum aimed at Laser Projectors...

Photonlexicon


Jerry

lasersbee said:

PL (Photonlexicon) is another Laser Forum aimed at Laser Projectors...

Photonlexicon


Jerry

Click to expand...

Thanx! :beer:

A while ago, I bought a 40A 5V Vicor PSU that has voltage trimming down to 2.5V. Sadly, I haven't had a chance to purchase a bar yet, but I was planning on using that with a current sensing resistor and some other crap. Obviously, 1mA accuracy isn't really needed when you're dealing with currents this high. I believe that the PSU cost me around $50.

jwc said:

A while ago, I bought a 40A 5V Vicor PSU that has voltage trimming down to 2.5V. Sadly, I haven't had a chance to purchase a bar yet, but I was planning on using that with a current sensing resistor and some other crap. Obviously, 1mA accuracy isn't really needed when you're dealing with currents this high. I believe that the PSU cost me around $50.

Click to expand...

That sounds like a decent deal indeed, but I need more than 40A.
I am taking the cheap way & building my own supply. I reworked a microwave oven transformer to supply 5V @100A, I have 4 100A diodes, & an 80,000µf bank of low ESR motherboard capacitors. To these I have to add a current regulator, metering, & transient protection.

Then all I have to do is build the TEC diode mount & it's controller.


BTW: A couple of clips of my last laser build project, a 20W CO2:
http://www.youtube.com/watch?v=dZnTWFF3RhgYouTube - Laser test
http://www.youtube.com/watch?v=WWrUbVvn7Kshttp://www.youtube.com/watch?v=AdLqtdaDHeY

tekwiz said:

The factory package had "overvoltage ~8V" hand written on it.

Click to expand...

Your typical multimeter uses 9V for a diode test.

Also, your above links are broken. I was able to extract proper links, but they do need revising.

Is it RF powered? Doesn't seem to be 20W to me, but I guess its impossible to tell from a video.

Thanx for the tip about the links. The laser is a sealed tube unit, DC powered. I was wondering about the power level myself, having nothing to measure it with. The tube is drawing the correct current, but I think the power may not be up to specs because of the fact that I am not using any filtering in the power supply, which would make for a pulsed beam, rather than steady. I have been thinking about adding filtering to increase performance. perhaps then I can cut metal with it. I can cut anything non-metallic, but no metals. This with a single GaAs focus lens. I do get a nice narrow kerf, around .5mm, with air as the blow gas. I have one of those GaAs lenses from PKU & was rather dissapointed that the FL was nowhere near what they specified.:tsk: If anyone has one of those, the actual FL is 1.750", not 2.500".
On the DMM diode test function: Just because the meter uses 9V as the test voltage doesn't mean that there will be 9V across a LD. The whole point behind the diode test is that the device under test loads the voltage down so it's Vfd can be measured. The test current is in the microamp region, which shouldn't harm a LD, unless the polarity is reversed. That's the way I see it, anyway.
As always, I invite discussion & comments.:yh: