SO... I'm staring at these labbies this morning thinking "Man, I need to find some sockets to fit the AC in pins for these" and THAT lasted about 30 seconds, next thing you know it's "sacrifice the extension cord ,solder, solder solder" (Not EXACTLY that bad, but close and the first fire of Labbie #1!
As shipped, the labbie fired consistantly to 80mW and held solid as a rock through 3 tests (up to 3 minutes each) so I decided to run a few "mean" tests to see what we could do. In my excitement, I forgot to log the first couple of tests, but the module climed smoothly to 118mW without a hitch (and I had already told myself I wouldn't run them over 100 for safety's sake - yeah RIGHT!) however, when shut down and restarted at this power, the module "strobed" instead of a nice steady beam until I turned the pot back...
Anyone want to chime in a more professional explaination?
Anyhow, I started to experiment with settings, and found that a setting of about 105mW gave me consistant operation (whew - nothing damaged) so I turned it back a bit and refired it, right back on 80mW, nice and comfortable, started the LB1 and slowly turned it back up to just over 100 (see attached graph), as of right now the laser is firing perfectly and running right around 103-104 without a hitch!
A few checks showed that the driver board definitely runs hotter at the higher settings, so I'm going to try and get this mounted in my fan-cooled enclosure later today and see if that gives it a bit more stability at higher temps, I'm also going to be messing with the modulation once it's in the box so I'll post more details then!
And a couple of pics to show the mounting layout, etc:
The reason the units "strobe" is due to two factors. The first is the fact that the conversion efficiency curve for a given KTP crystal is nonlinear. As you alter the pump power, the efficiency will also change, only not linearly (not a smooth sweep like the current change as you turn the pot). Instead it may fluctuate rapidly until you find a stable spot.
The second factor is the fact that those driver boards are decent but not great. The pot may be a little noisy.
If you combine these two factors you end up with a nice (sort of) strobe effect as you turn the pot.
You may believe that you need active cooling on that MOSFET on the driver board. It does run hot, but that component is rated to 150C, and I can guarantee you that as hot as it is, it is nowhere near that hot. A fan is a good idea, but not necessary.
Thanks, EF - the pots are REALLY touchy, so you may be right on both points... I'll take some time and play once I get the enclosure and mounts all set up, my goal is to find a sweet spot right around 100mW for these.
I got a couple of these from Axixz, one is doing 135 mW, (it's mentioned in my sig.), the other has a tough time getting over 80 mW, I would like to find an improved driver as well. But for the $ these are hard to beat!
They are 500mW c-mounts. I've replaced one with a 1W FAC corrected c-mount and it works great with a fan blowing on it. Gotta have active cooling of some sort, though. You could even mount the entire laser head on a TEC. I'm getting about 150-200mW out depending on how it feels when I take the measurement.
^The original diode was FAC corrected, so I replaced it with the same. Also I'm running the pump at about 750mW (give or take) for added lifetime. I know that I could pretty easily ruin the crystals at that power, but with a $65 laser I'm not too worried.. Thanks for the warning, though.
Just a tip for those that want to use a connector, instead solder the wires on the board (power supply).
The connector looks similar to an AMP one ..... i can't grant you that you can find it in any PSU, but lots of the old types PC power supply had this exact connector inside, for the main power section ..... so, if you can find some old dead pc power supply to mangle, and if you're lucky .....