First, electrical energy is pumped into the atoms; this process is called Population Inversion. The excited

atoms send off photons which hit more atoms and cause a landslide of more photons. Next, mirrors are added

to every energy pump to bounce the photons back and forth along one direction through the atoms. Eventually it

builds up into a bigger and bigger wave or clump of photons. Reflective mirrors are used on one end so that

some of the light leaks through. Once enough atoms are excited they begin to "lase". The beam inside the laser

is more powerful than the beam that comes out. All this happens very quickly with just a flick of a button a laser

can be turned on.