| This applet illustrates
a schematic operation of a laser. The yellow photons represent the pumping radiation. The group
of red photons is the coherent laser beam. The
balls mark the atoms making transitions between three energy levels. The
pumping radiation couses the transition of atoms from the ground state to
the high energy excited state. From this short-living state the atoms go
by non-radiative transition to the long-living metastable state. Once in
the metastable state many atoms can be accomulated. The laser beam, stimulated
emission, arises when all atoms simultaneously make a transition to the
ground state.
|