Yes yoonie, as GSS said, the trade off for having a small host is short duty cycles and frequently recharged batteries. There was a thread on here a long while back where someone made a 3W laser into a host the size of a zippo lighter, using a button cell battery. The Lasers power is determined by the diode and driver, host size is irrelevant. But if you dont want the laser to overheat in a matter of seconds and want the battery to last more than 5 or 10 minutes you'll want something with bigger batteries and a bigger heatsink, I personally like copper heatsinks for lasers over 1W, and especially for over 3W. 10440 batteries are I believe, the size of a AAA
Tung, can you turn the current to 1.8A instead of 2A? Is it easy to do? If it's not too much trouble and you can do it, let me know, and let me know the power output at 1.8A. Do that and I'll buy it