In reply to Jones Beene's message of Thu, 13 Mar 2008 07:48:13 -0700 (PDT): Hi, [snip] >This radiation can even be made semi-coherent by using some forms of carbon >(graphite) as the sink (target) since forms of graphite (despite its blackness >;-) is not a blackbody radiator, and emits mostly in a single preferred >spectrum. [snip] This made me think of something else: Preferential absorbers have been made that have a fairly sharp transition point, e.g. above which they radiate/absorb strongly, and below which they radiate/absorb only very weakly. Now suppose one also had a substance in which the absorption profile was reversed. Two thin layers, one of each would overlap in a sharp peak.
Just what you are looking for, although even at a single frequency the radiation still wouldn't be coherent (i.e. all in phase). For that you need a resonant structure that superimposes a phase relationship on the emissions. (Akin to electron bunching in a magnetron). Regards, Robin van Spaandonk The shrub is a plant.
