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Re: combining laser beams



On Thursday, Dec 12, 2002 Herbert H Gottlieb wrote:

Ludwik Kowalski writes:

I forgot to add the obvious, the "amplifier" must received
energy to populate excited levels. I suppose this can
be done with visible non-coherent light.

Please explain a possible mechanism by which non-coherent
light can provide the energy to to populate ther excited levels
Has it ever been done already? If so, where can I find out
more about it?

JohnG and BobS already answered. Let me add that the
mechanism is spontaneous emission. Photons of visible
light are energetic enough to excite atoms to numerous
levels above the metastable level responsible for "lasing".
The "lasing" level is populated by spontaneous decays
from many (but not all) levels above it. The non-coherent
light may come, for example, from a coiled xenon
discharge tube, or from a window. The amplification is
probably proportional (up to a point) to light intensity.
Ludwik Kowalski