I worked with high power lasers in grad school. I used a laser powerful enough to set things on fire. The laser used so much power we had to build a plumbing system with 3/4" pipe which ran at full capacity.

Point it at piece of wood and it will catch fire. Point at a mirror an the beam bounces off and doesn't do a thing to a mirror. In fact we had an optical table and ran the beam all over the place with mirrors.