Marcia,

For the technical question, as it wasn't obvious what he was driving at. Best way to make an overunity laser is to make the overunity power system for it, and try to make it self-powering, since a laser system must include a source of power.  If by "TM wave" he meant "traverse magnetic" wave, any wave can be coherent under the right circumstances.  The wave is actually a coherent entity itself, moving or occurring in the medium's particles, etc. and thus requires coherence in those movements. In short, a "wave" already is a "coherence" phenomenon.

Cheers,

Tom