I believe that I have come up with a working model of a real life light saber. This model might maybe deliver enough energy to toast a marshmallow or pop a party balloon as it is just a proof-of-concept. If it works, however, then substituting infrared lenses and using a heat source in the handle we get something more powerful, i would think. Here is the listing:
http://www.thingiverse.com/thing:277209
Attachment 796
Attachment 797
It is basically a lens assembly with an adapter that snaps onto a high intensity flashlight. Descriptions of how it is supposed to work are in the thingiverse listing. I'd be interested to learn what you think of it...
Les