Research Copyright 1998 Lucent Technologies. Contact the webmaster . A laser is a device that creates and amplifies a narrow, intense beam of coherent light.
Atoms emit radiation.
Normally, they radiate their light in random directions at random times. Reflective surfaces at both ends of the cavity permit energy to reflect back and forth, building up in each passage. This process is called stimulated emission . The bombarding photon and the emitted photon may then each strike other excited atoms, stimulating further emission of photons, all of the same frequency and phase. This process produces a sudden burst of coherent radiation as all the atoms discharge in a rapid chain reaction.