IIRC, there were a few threads on this in the past. It's not practical to do, all that happens is that the popcorn is burned. I think someone tried to shine three lasers on different sides of the popcorn, and it still just burned.
I've burned my fair share of popcorn with lasers. The problem is the physics of popping corn. In order to pop a kernel the internal temperature of the endosperm must be superheated so that the kernel ruptures and the dense starch expands and basically turns itself inside out. Well a laser provides energy incident upon the pericarp and not the endosperm so the kernel just burns. The kernel needs even heat across the entire kernel without having high energy densities that lasers provide.