Module 7 : Laser- I
Lecture   : Introduction - Basics of stimulated emission
 

incident radiation $ \nu$is given by

        $\displaystyle \nu = \frac{E_f-E_i}{h}$
If this condition is not satisfied, the matter becomes transparent to incident radiation.

 
\includegraphics{laser2.eps}
  Spontaneous Emission:
  Atoms which are in excited states are not in thermal equilibrium with their surroundings. Such atoms will eventually return to their ground state by emission of a photon. If $ E^\ast$is the energy in the excited state and $ E$the energy of a lower lying state (which could be the ground state), the frequency of the emitted photon is given by
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