Flashlamps surround rods of one-inch thick disks of glass containing neodymium ions. Light from the flashlamps stimulates coherent emission of light from it. This makes the light more powerful. Coherent light consists of waves in a fixed relationship to one another, synchronized with one another. In contrast, incoherent light waves are not synchronized.
Laser light is coherent.
A form of the atom or element hydrogen. Deuterium is sometimes called heavy hydrogen. Its nucleus has one proton and one neutron. Deuterium can easily be found in water, making it an abundant fuel for fusion energy. This device protects a laser amplifier chain against light reflected back through it.