d. The words stimulated and emission go together. The concept comes from
nature. If the sun can store energy in coal, then surely a laser can store energy until
there is enough to make a laser beam. Therefore, a laser is pumped so full of light
energy that it cannot hold it all. Some light particles escape simultaneously setting
other light particles free. That is, one light particle stimulates the emission of another
Figure 2-9. Simulated emission.
e. The word radiation refers to the fact that the energy released by the laser is
in the form of radiating light waves. Light waves are sometimes called photons, a word
which means a small bundle of light. These particles of light energy radiate out from
their source in a straight line.
Figure 2-10. Photons.