Optical amplifiers boost light directly using a quantum mechanical effect known as stimulated emission. This principle dictates that a photon can interact with an atom already in an excited energy state, forcing the excited atom to immediately release its stored energy as a second. Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes. Typically, inputs and outputs are laser beams (very rarely other types of light beams), either propagating as Gaussian beams in free space or in a fiber. The loss occurs primarily due to two physical processes within the silica glass fiber: absorption and scattering. Absorption occurs when impurities. A laser is created when electrons in the atoms in optical materials like glass, crystal, or gas absorb the energy from an electrical current or a light. That extra energy “excites” the electrons enough to move from a lower-energy orbit to a higher-energy orbit around the atom's nucleus.
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