[Application of laser surgery in veterinary medicine. 1. Fundamentals]

This article will outline the key words of laser physics. Albert Einstein set the basics of laser physics by characterizing the principles of stimulated emission of radiation in 1914. An excited atom can change from these excited energy level to a lower level by emitting energy in form of photons. If this photon strikes another excited atom, it will stimulate emission of another photon. By these action two identical photons will emerge. An optical resonator is used to amplify the stimulated light emission coming from a laser medium. Laser differs from other light sources in three important properties: coherence, collimation, and monochromasia.