Laser is an acronym for light amplification by stimulated emission of radiation, which means light is amplified before it is released as synchronized waves of electromagnetic energy that form of a tightly-focused beam of light. Lasers and their precursor the maser are based on theories of stimulated and spontaneous emission of electromagnetic radiation first proposed by Albert Einstein in 1917.
From the 1930s to the 1950s, various scientists attempted to develop functional laser and microwave maser devices. Until the first laser was developed in 1960, the competition, urgency, and pressure to reach the goal was comparable to a multi-national space-race. In the Soviet Union, Nobel-winning physicists Aleksandr Prokhorov and Nikolay Basov were rushing to develop laser and maser devices. In the U.S., Bell Laboratory employees Charles Townes and Arthur Schawlow were favorites to win the laser race through ample funding from the Bell Telephone Company. Columbia University graduate, and physicist for Technical Research Group Gordon Gould was also hot on their trail. Almost simultaneously, Prokhorov, the Townes and Shawlow team, and Gould hit upon the same solution, which they scrambled to patent. For the next three decades, Gould (the first to coin the term laser) contested the patent rights of Bell, Hughes Research, and several other companies.
To produce a focused beam that is capable of traveling great distances, atoms and electrons must be manipulated to produce consistent wavelengths with identical frequencies, phases, and alignment. Einstein proposed in his theory of stimulated emission that atoms could induce identical atoms to release energy in the form of light. Scientifically, heat, light, and electricity are forms of energy. In lasers, atoms are charged by an intense flash of light that stimulates electrons and pushes atoms from ground-state to levels of excitation. Eventually, these excited atoms must return to the relaxed ground-state. To do so, they release their excess energy in the form of photons. When one atom releases a photon or a unit of light, it triggers a chain-reaction where nearby atoms also release their photons. To produce the concentrated laser beam, light is amplified by mirrors that reflect wavelengths through a gain medium, such as ruby crystal impregnated with chromium or reactive gases, before the beam is emitted through a semi-mirrored aperture.
Today, the smallest diode lasers are used in CD players, DVD players, laser printers, and hand-held laser pointers. Lasers with varying frequencies have also been used for welding, precision cutting, high-tech electronics, medical and cosmetic procedures as well as missile and defense systems.
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