I've built two lasers. Ever focused sunlight with a magnifying glass? It's basically the same thing. The focal point of the beam that is powerful enough to heat or burn objects is so small that you could vaporize single crystals of DMT at a time. But in order to heat up all your DMT in an efficient enough manner to not waste any while still inhaling enough for a dose you would have to use multiple lasers at the same time. Also just moving your laser 1/16th of an inch either closer or farther away and your out of the focusing point. Which means no heat.

Also you have to understand safety is extremely important with lasers that are capable of burning or even heating. A normal store bought laser is <5 milliwatts. A laser capable of sufficiently lighting a cigarette would need to be >300 with the green diodes and >500 with diodes around the ultraviolet and infrared spectrum. These laser WILL temporarily blind you if you manage to get the light in your eye either directly or indirectly via ANY reflective surfaces for a second. A couple seconds, and you might have permanent damage.

You would be surprised how reflective things are that you didn't think were reflective. Shining my laser around the room and I got blasted a couple times in a row.