Diode Laser engravers are quite common in specialty equipment. While I have posted in other forums about this subject, there are serious safety precautions people need to observe prior to powering up these devices:

1. Two pairs of safety glasses for the range of possible output colors/spectra your laser emits (you get 1 chance to lose your eyesight from a reflective surface)
2. Don't trust the glasses anyway, as some long-wave IR can penetrate a few cm into your flesh to cause internal burns (imagine a sunburn in 3D).
3. Use a metal enclosure with a web camera to monitor for work-piece fires.
4. Make sure to have a dry-chemical fire extinguisher next to the machine
5. Diode lasers are expensive, but few know how to handle them without damage. Use a physical lock-switch to disable the laser with a key, and ensure the machine has a mushroom safety switch on the main power box.

I have driven 35W fiber OSRAM laser modules using the following:

1. Reverse 10A schottky diode on laser tabs, as they are very sensitive to static discharge and have minimal back-emf tolerance
2. Inline 100W 0.5 ohm current limiting resister (10A 5v, used to adjust current without laser in circuit like a shunt)
3. Modified the older ATX supply as typically these models had more current available on 5v rail.
4. Adjust the regulated 5v line voltage down to the laser specs while measuring the drop across the mostfet, resister, and wires. This model specific mod also used 6 parallel wires to handle the various loads we tested.

For a below <30W diode lasers, I would recommend using a modern "300W 20A Step down Converter" low-ripple switching buck-regulator module off ebay with constant-current (CC) and constant-voltage (CV) adjustments. And add a few extra 1000uF 16v smoothing caps across the regulator output lines.

There are also constant-current LED ballasts available, but you need to closely inspect the laser manufactures specifications to see if it is safe to run above 2.8v. Usually high-power Diode lasers do not work like regular Diodes at all (a lot of people ignore this fact), and must also have active cooling with a water block (or TEC) to avoid warping the internal optics.

300W 20A Step down Converter example:

• Input Voltage: 12V DC
• Output Voltage: 2.8V DC
• Output Current: 10A max (start at 80% of lasers power)
• Efficiency: <95%
• Output Ripple: <=50mV (very important)

Note: At 2.8v this driver will max out at 5.6A (or about 16W output), so in order to get a maximum 10A (28W output limit) this design should parallel up two 100W 0.5ohm resisters.