M_a_r_c wrote:
> Is not a laser an excitated resonant optical cavity eg a oscillator?

No. You have to pump up the electrons into higher valences, and then 
when one photon hits, it causes the excited atom to drop the next photon 
at the same frequency and phase, because that's how the math comes out 
for photons. (It's the opposite for electrons, which is why you can't 
have more than two electrons in the same place and phase and all.)

The resonance comes from putting a mirror at each end to get the photons 
crossing the substrate more than once, so they have a better chance of 
hitting more atoms. But in theory, it would work if you just made a 
sufficiently long tube, or you could keep the atoms pumped up without 
interfering with the emmision. (The latter is what laser LEDs do, I think.)

-- 
   Darren New / San Diego, CA, USA (PST)
     Remember the good old days, when we
     used to complain about cryptography
     being export-restricted?

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