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In laser physics, gain or amplification is a process where the medium transfers part of its energy to the emitted electromagnetic radiation, resulting in an increase in optical power. This is the basic principle of all lasers. Quantitatively, gain is a measure of the ability of a laser medium to increase optical power. However, overall a laser ...
The active laser medium (also called a gain medium or lasing medium) is the source of optical gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy state from a higher energy state previously populated by a pump source. Examples of active laser media include:
The gain medium is the major determining factor of the wavelength of operation, and other properties, of the laser. Gain media in different materials have linear spectra or wide spectra. Gain media with wide spectra allow tuning of the laser frequency.
Laser gain medium and type Operation wavelength(s) Pump source Applications and notes Dye lasers: 390-435 nm , 460-515 nm (coumarin 102), 570-640 nm (rhodamine 6G), many others Other laser, flashlamp Research, laser medicine, [2] spectroscopy, birthmark removal, isotope separation. The tuning range of the laser depends on which dye is used.
The back-formed verb "to lase" is frequently used in the field, meaning "to give off coherent light," especially about the gain medium of a laser; [16] when a laser is operating, it is said to be "lasing". [17] The terms laser and maser are also used for naturally occurring coherent emissions, as in astrophysical maser and atom laser. [18] [19]
Optical gain is the most important requirement for the realization of a semiconductor laser because it describes the optical amplification in the semiconductor material. This optical gain is due to stimulated emission associated with light emission created by recombination of electrons and holes .
The photon of an incident laser pulse (pump) is, by a nonlinear optical crystal, divided into two lower-energy photons. The wavelengths of the signal and the idler are determined by the phase matching condition, which is changed, e.g. by temperature or, in bulk optics, by the angle between the incident pump laser ray and the optical axes of the ...
The linewidth of the laser's emission also becomes orders of magnitude smaller above the threshold than it is below. Above the threshold, the laser is said to be lasing. The term "lasing" is a back formation from "laser," which is an acronym, not an agent noun.