An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the visible, infrared, or ultraviolet regions of the spectrum. They are capable of producing immense heat and power when focused at close range and are used in surgical procedures, in diagnosis, and in physiologic studies. Lasers used at low power, transmitting light not heat, have been used in wound healing and pain control (LASER THERAPY, LOW-LEVEL).