Andwhat's moreamazingisthatif a solitaryphotonpassesbyanexcitedatomthatcouldemitanotherphoton, there's a goodchanceitwillemitonebecausethetwophotonswantbetogether - evenbeforethesecondoneexists.
Soonceyouhaveallthesefriendlyphotonsbouncingaroundbetweenthemirrors, youcanjustopenup a littleholeattheendandletout a blindingstreamofcoherentlight - a laserbeam.