The most efficent lasers are about 10% efficent. Plus there of a given single spectrum freq. They do not produce any frequency than what there tuned freq.. Co2 have the highest % and gas fueled are next. Lasers produce power by using so much power and with a coating on each end to give the required light. I would guess that that hand laser puts out .5 mw. If its one of the real expensive kind. The dia is usualy .032 dia. so you only need roughly 30 per sq. in. roughly 1 watt if power pre sq in . so roughly 4320 per sq ft.
That would only take 12,960 batterys per sq ft.
I would just wait till H3 goes on sale , under $300,000 a truck load and build a gas fired laser. This way you will save money , and not need to joke around.
Giga watts lasers are more fun than HeNe beams, or electronic bulbs.
Never go near the edge of the earth , you can always fall off.