Re: combining laser beams

["Carl E. Mungan" <mungan@USNA.EDU>]

John gave us beans:

> If you define brightness as the amount of
> energy per unit area per unit solid angle,
> then Liouville tells us that brightness is
> conserved by any apparatus where you can
> keep track of the whole phase space (i.e.
> excluding absorbers and emitters, which
> do of course uphold Liouville's theorem
> but for which a detailed analysis is beyond
> the scope of this note).

Perfect! This is exactly the right spirit of discussion on the theory
side of the issue. Now, can you me some pointers on what restrictions
Liouville puts on absorbers and emitters? This is indeed what I was
coming to next. It certainly seems that a laser amplifier increases
brightness of the optical beam at the expense of the entropy dumped
out as waste heat. Carl
--
Carl E. Mungan, Asst. Prof. of Physics  410-293-6680 (O) -3729 (F)
      U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5026
mungan@usna.edu    http://physics.usna.edu/physics/faculty/mungan/