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sp04 - inversion intrinsically a non-equilibrium condition...

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Lasers are a natural choice as a Spectroscopic  tool.  But what exactly are they?
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We can put energy into matter to ‘store’ it for amplification  (gain) 
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What goes up must come down:  Spontaneous emission! But you can’t use this to amplify light --- this is incoherent!
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Einstein was the first to recognize that there must also be a  another way for the stored energy to be released, the  microscopic reverse of absorption: Stimulated Emission!
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So:   L ight  A mplification by  S timulated  E mission of  R adiation Seems simple, but how do you get  net  amplification if  absorption is ALWAYS present, and competes with the  Stimulated Emission?  Need more population in upper level than the lower  level:  a population 
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Unformatted text preview: inversion , intrinsically a non-equilibrium condition. Negative Temperature??? How do you do that? What determines the photon energy of the LASER? It could be the characteristic of the gain medium, or, it could be determined by the cavity (resonator) if the gain is broad enough. The ‘storage time’ of the laser cavity can make this wavelength selection very precise! What is thing called Q?? A Q-switch (pulsed) or Output Coupler (CW) is necessary to get the light out of the laser cavity so that it can be used for spectroscopy. Components of a Laser 4) Gain 5) Resonator 6) Output Coupler / Q-switch What can you use a LASER for? Fin...
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