I'm already getting rusty on the laser stuff, and will have to brush up. What I can tell you though, is that similar to LED's, laser diodes will have a steep VI curve once you start getting much past the diode's "rated" Vf. Beyond that, current will drastically go up with only small changes in voltage. I believe the regular 'ol application of Ohm's Law does not apply here. If someone can explain this more thoroughly, or clearly, please do.
Be careful! They can blow very quickly, with no warning. At least with an LED, you have a chance to cut the power when you see the blue shift. Not so with laser diodes.
My reddie, made with a 16X burner diode ("typical" ratings are 2.7V @ 150mA to produce 80mW continuous wave), uses a 2.7 Ohm resistor for current limiting, and a 100uF, 6.3V cap in parallel with the diode legs for psuedo soft-start. I've not measured current on 2 X AA alkalines, but they'll definitely keep the diode safe. Always wanting more power though, I stuck in 2 Energizer lithium's, and measured current at approx. 310mA. That boosted things up a bit! Pops balloons without using a sharpie.
Granted, I don't play with my lasers that often, but I've only blown one diode with the lithiums, and it MIGHT have to do with the crappy momentary switch I was using, as opposed to the overdrive... or possibly a combination of both? :shrug:
Hope that helps!
