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Schematic diagram of a typical laser, showing the three major parts. A laser is constructed from three principal parts: An energy source (usually referred to as the pump or pump source), A gain medium or laser medium, and; Two or more mirrors that form an optical resonator.
Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When for a period of time the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited state, population inversion ...
A four-level laser energy diagram. Here, there are four energy levels, energies E 1, E 2, E 3, E 4, and populations N 1, N 2, N 3, N 4, respectively. The energies of each level are such that E 1 < E 2 < E 3 < E 4. In this system, the pumping transition P excites the atoms in the ground state (level 1) into the pump band (level 4).
In laser physics, such a material is called an active laser medium. Combined with an energy source that continues to "pump" energy into the material, it is possible to have enough atoms or molecules in an excited state for a chain reaction to develop. Lasers are distinguished from other light sources by their coherence.
Laser types with distinct laser lines are shown above the wavelength bar, while below are shown lasers that can emit in a wavelength range. The height of the lines and bars gives an indication of the maximal power/pulse energy commercially available, while the color codifies the type of laser material (see the figure description for details).
A ruby laser most often consists of a ruby rod that must be pumped with very high energy, usually from a flashtube, to achieve a population inversion.The rod is often placed between two mirrors, forming an optical cavity, which oscillate the light produced by the ruby's fluorescence, causing stimulated emission.
Laser rods (from left to right): Ruby, alexandrite, Er:YAG, Nd:YAG. A solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid as in dye lasers or a gas as in gas lasers. [1] Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers, called ...
Optical pumping is a process in which light is used to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher one. It is commonly used in laser construction to pump the active laser medium so as to achieve population inversion. The technique was developed by the 1966 Nobel Prize winner Alfred Kastler in the ...