laser

1. A device that produces a high-irradiance, narrow-spectral-width, coherent, highly directional, i.e., near-zero-divergence, lightbeam by stimulating electronic, ionic, or molecular transitions to higher energy levels so that when they drop back to lower energy levels they produce a stream of photons of various discrete energy levels. Note 1: The word “laser” is derived from “light amplification by stimulated emission of radiation.” Note 2: The lasing action is produced by population inversion. Note 3: The release of radiated energy can be controlled in time and direction so as to generate an intense highly directional narrow beam of spatially or temporally coherent electromagnetic energy, i.e., the electromagnetic fields at every point in the beam are uniquely and specifically definable and predictable. Note 4:The coherence degree of laser radiation can exceed 0.88. The lightbeam emitted by a laser is suitable for launching optical power into optical fibers. The beam can be...