I would recommend the 1000mah rechargeables. they give great power and last long. Lithiums are also very good and probably give the best burning power, however the rechargeable batteries can be used more than once... I've never seen 1.8V batteries though...
Yes, the 3.6V lithiums will kill your laser.
Unless you mean 3.6V total?
There are 3.6V lithiums in the AAA size... 2 of those will kill your laser but it should be able to run on 3.6V total... so 2 1.8V should be ok. But it depends on how good the driver in your laser is.
Yes, I meant 3.6V total, and I\'m not too sure of how good my laser is. Ill probably buy the rechargeables, and 4 AAA Lithiums for comparison. And I don\'t want to take chances with the driver, so I\'ll stick with 3Vs total.