Jump off the train. These things are dangerous. They also probably have a gazillion hours of operation on them which makes them electrically brittle, and sensitive about their age.
One of the things I often see on EEVBLOG is that laser diodes are described as glorified LEDs that can be ran off a current limiting resisitor. The issue with this is they are amazingly sensitive to short spikes that will not harm a LED, but will blow the reflecting faucets off the ends of a laser diode chip and turn them into lousy damaged leds... Those of us who use these for our day job go out of our way to drive them from pure current sources with soft starts, voltage clamps, protective limit circuits, and careful arangements to close the current control loops before applying any energy to the diode itself.
If I had a dollar for every LD I've seen or heard of a bench supply blowing, I'd have enough money to fly to Straya, meet Dave and marry a good looking Aussie chick. Especially the supplies with tap changing relays in them or little 20 to 200 uF caps across the output terminals at all times.. If it comes up in an undefined state, it is NOT an LD driver..
First thing, get a Lasorb across the laser diode.
www.lasorb.comThis protects it against spikes. I know its a huge LD chip and you would think that a burst of static will not kill it... Wrong.
You have a fiber coupled laser diode. We refer to the 974 nm wavelength laser diode as "PUMP" diodes. IPG uses them in their lasers to pump a lasing fiber that lases at a different, longer wavelength. Basically store the energy as an upper energy level in a dopant metal ion in the fiber, for about 250 some microseconds, then dump it out in a few 10s of nanoseconds. So you have the continuous Pump Laser for a Pulsed Fiber Laser that uses Q-Switching, which you can think of as a form of pulse compression of sorts, the optical equvalent of dumping out a capacitor. So a typical IPG laser would have many modules like yours pumping a long fiber laser, and a Q-switch module to block the fiber laser from lasing until enough energy is stored in it to dump a pulse. The high peak power in a short duration is what is useful, and at these wavelengths, quite scary.
Now for the worrisome part on my end.. Please buy a quality pair of Laser Safety Goggles for yourself and anyone else who may be in the room. Including your wife, children, coworkers, friends, garbageman, dogs and cats..
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=762You need a certified goggle, not a untested, uncertified 50$ Chinese clone goggle from Ebay or Amazon.. Preferably OPTICAL DENSITY SIX OR GREATER!
Then find a nice black and white CCD camera and remove the IR filter on it and use it for alignment, etc.. 974 is down at the far end where silicon and CMOS have a still useful but very weak response. Back reflections, even weak ones, will easily fry pixels in the camera/lens combination.. Trust me on that, too...
Even if you totally enclose everything, you want the goggles.. Trust me on that...
Make me happy and toss that thing in the trash...
Even diffuse and specular reflections from that diode can be a hazard. When is laser light not a hazard? Well only when totally contained and when the scattered light has been profiled, measured, documented and checked against the rules, and when the design is checked by another laser safety professional.
That 970 nm wavelength likes to go through skin until it finds nerves, blood vessels, bone, immune system or muscle tissue, and then it it frys it. It is also an excellent eye hazard...
You only see IR TWICE...
It also has a habit of damaging your peripheral vision without you noticing it, well, until the truck hits you...
Next up, when the seller removed those things from the fiber laser, he roughly cleaved the fiber, but did not polish it. This means you now have a laser diode that may have a distorted output when collimated. Usually we cleave them at an angle to prevent back reflections into the diode and then polish the end. So you have NO idea how that beam is exiting the fiber, or where it exits the fiber, or if it has ever been bent less then the minimum bend radius for the fiber. IF the exit fiber breaks or partially cracks,, you have one hell of a hazard elsewhere, too.
Yes, under certain conditions, LDs are really sensitive to back reflections, and in the fiber laser, that thing probably had a optical isolator on it..
Also, trust me on this, not a good laser for stripping paint.
You have a burner / engraver / modestly lousy cutter, unless your cutting / burning tissue...
There is a forum member here who will PM me to remind me I should have just stuck to the safety and let you quickly blow your diode for his, and my, peace of mind. Often I agree with him...
The power control on that laser would have been done with a beam sampler elsewhere in the larger system, so you just have a fiber coupled laser diode module.
BE CAREFUL... Be more then careful, be downright paranoid about Laser Safety. PS, Vent the cutting fumes, they are incredibly toxic.
Steve