Driver for this 2W 735 nm diode?

[runcyclexcski]

Hi all,

I got myself a 9 mm can emitter at 735 nm... it's still a relatively exotic WL, I guess, as a search for 735 yielded 0 results!

I could not get it as a module for cheap: a turnkey one from coherent etc would be several K. So I got just the can, and I would like to drive it with a generic driver. This will be operated in CW for hours at a time. I got a generic heatsink with a fan, and a 3-component IR-rated glass lens. Mounted the chip with acrtic silver. I am quite ignorant about electronics though... Could someone recommend a relatively fool-proof driver (e.g. that would protect it if I get the polarity wrong, or smth stupid), and what to look for? I got a generic driver which I currently use to power a 1W 450 nm diode (12V in, fan, TTL, the usual), but I am hesitant to plug the 730 can in as it was quite pricey. Also, cables and plugs that this driver comes with do not look like 2amp rated at all, but what do I know anyway...

BTW, a lead on how to stick this into a fiber to get a more gaussian-like spot out would be great, too!

Here are the specs

LDX-3215-735
735 nm
9mm package
2,000 mW output
threshold 600 mA
operating mA 1800
operating V: 1.9

... from here:
http://www.rpmclasers.com/wp-content/uploads/products/LDX 730-885nm Laser Diodes.pdf

Cheers!

 

[paul1598419]

That's got a very low Vf. I'd use an 808nm driver as that should work fine and they aren't terribly expensive either. IDK, about a totally fool proof one, though. If you are putting this into a lab host, you should use a wall wart to supply the driver. Are you planning on driving it at 1.6 amps? That is what seems to be recommended.

 

[10fenny]

735? That sounds cool!! But as far as lasers and drivers go there is really not much of a fool proof answer.. Paul suggested a good driver. I also recomend you do some research on your project before you blind or burn something.. but your profile states 2015 entry with 5 posts... so idk how to approach this.

 

[paul1598419]

Yes, this should be a deep red color, but at or near 2 watts it should be quite visible. Any driver that would work for a 2 watt 808nm in the near infrared should do the job. It seems that you aren't well known here even though you joined at the end of 2015. I expect you should know the basics about laser diodes or you wouldn't try to tackle this job. Since you already have the diode, I hope you have a way to press it into whatever module you will use with your lab host. To set the current you will need a dummy load to take the place of the laser diode while setting the current to 1.6-1.8 amps. If you have any other questions feel free to ask.

 

[runcyclexcski]

Thanks a lot for your answers, both, they are very helpful! I also spoke to OdicForce on the phone (I got the drivers from them), and they were very helpful in explaining how to approach this. As you suggested, they recommended putting together a dummy load, which is what I am going to do.

Regarding safety and seeing 735... I have a IR vision device with PMT tubes which sees 735 very well (I already have two low-power 735 units which were turnkey... had 100x less power, and costed 10x more than this LDX, and this LDX was $700. ). I have protective goggles with a cutoff above 600. So I won't be relying on eye-balling to check if a 2W invisible laser is on . I have colleagues with holes in their retinas (they are physicists, I am a biologist/bad_hacker).

You are right, I joined in 2015, but I am not a 'true' LP enthusiast: I use lasers as turnkey, but if they are too exensive, try to hack smth quickly as a proof of concept when there is an urgent need (like the 735). Once it works OK-ish, I move on to other things, and write a grant to buy the unit as a whole (safety features etc). E.g. a 730 nm fibre laser from MPB at 500 mW output is 30K. Any takers?

 

[runcyclexcski]

To set the current you will need a dummy load to take the place of the laser diode while setting the current to 1.6-1.8 amps. If you have any other questions feel free to ask.

Paul -- May I ask what I can do to test the orientation of the diode when plugging it in, w/o destroying it? I stupidly did not label the cables, they got twisted, and it's already sealed in my heat sink...

 

[paul1598419]

Are you saying that you no longer know which pin is the anode or cathode? The best way is to look it up, but if you sealed it and don't remember which wire goes where it becomes very complicated and not without dangers. The Vf if 1.9 VDC, so a voltage of a little less than 1 VDC should be used at minimum current. Take your best guess and if you don't see light immediately...stop. Try a different hook up and see if you get light. This is not a good way to do this, but if you are lucky, it won't kill your diode if you manage to guess wrong the first time. I would personally try to take it apart to see where the wires go, but if you can't.... this is probably your best way to try to find out.

 

[runcyclexcski]

Hi Paul -- yes, quite embarrassingly, I do not know which cable is which. That said... the heat sink its not very deep, so I can shine light inside and take the best guess. Then I will drive it at 0.6A (for which I would need to set my driver first, using the dummy load -- correct?), and try to see the light. My PMT tube device should help with that... by eye it would be hopeless.

 

[paul1598419]

No, I think 600 mA is far too much to use when trying to find out which leads are which. I'd start at 40 to 50 mA at 0.9 VDC and go from there. Hopefully that will be enough to get light while not being enough to damage the diode if connected incorrectly. I would only leave it connected like this for a second. If you are going to see light it will be immediate. Be careful, as you don't know, now, how this is supposed to be connected.

 

[runcyclexcski]

Paul -- OK. Then, I will start at 0.025 A, try both orientations, if no light either way, go up a notch, and try both orientations at each step.

 

[paul1598419]

Next time take copious notes. You'd be surprised how important that is. Leave nothing to chance. Doing it that way is dangerous and you risk the loss of the diode. If you have a certain hook up that you believe is right, try increasing the current there rather than going back and forth. It is less dangerous. But, don't keep increasing the current if you don't get light at 75 mA.