Toward the 20th century's end, one of the few lingering constraints was removed by a device that is both laser and fiber. For all the marvelous transparency of silica glass, light inevitably weakens as it travels along, requiring amplification from time to time. In the early years of fiber optics, the necessary regeneration was done by devices that converted the light signals into electricity, boosted them, and then changed them back into light again. This limited the speed of transmission because the electronic amplifier was slower than the fiber. But the 1990s saw the appearance of vastly superior amplifiers that are lasers themselves. These optical amplifiers consist of short stretches of fiber, doped with the element erbium and optically energized by an auxiliary "pump" laser. The erbium-doped amplifiers revive the fading photons every 50 miles or so without the need for electrical conversion. The amplification can occur for a relatively broad range of wavelengths, allowing roughly 40 different wavelengths to be amplified simultaneously. For the most part the devices that switch messages from one fiber to another (as from one router to another on the Internet) still must convert a message from light to electricity and back again. Yet even as researchers and engineers actively pursue the development of all-optical switches, this last bottleneck scarcely hampers the flow of information carried on today's fiber-optic systems. Flashing incessantly between cities, countries, and continents, the prodigious torrent strains the gossamer web not at all.
1917 Theory of stimulated emission Albert Einstein proposes the theory of stimulated emission—that is, if an atom in a high-energy state is stimulated by a photon of the right wavelength, another photon of the same wavelength and direction of travel will be created. Stimulated emission will form the basis for research into harnessing photons to amplify the energy of light. 1917 Theory of stimulated emission Albert Einstein proposes the theory of stimulated emission—that is, if an atom in a high-energy state is stimulated by a photon of the right wavelength, another photon of the same wavelength and direction of travel will be created. Stimulated emission will form the basis for research into harnessing photons to amplify the energy of light. 1954 "Maser" developed Charles Townes, James Gordon, and Herbert Zeiger at Columbia University develop a "maser" (for microwave amplification by stimulated emission of radiation), in which excited molecules of ammonia gas amplify and generate radio waves. The work caps 3 years of effort since Townes's idea in 1951 to take advantage of high-frequency molecular oscillation to generate short-wavelength radio waves. 1958 Concept of a laser introduced Townes and physicist Arthur Schawlow publish a paper showing that masers could be made to operate in optical and infrared regions. The paper explains the concept of a laser (light amplification by stimulated emission of radiation)—that light reflected back and forth in an energized medium generates amplified light.
1960 Continuously operating helium-neon gas laser invented Bell Laboratories researcher and former Townes student Ali Javan and his colleagues William Bennett, Jr., and Donald Herriott invent a continuously operating helium-neon gas laser. The continuous beam of laser light is extracted by placing parallel mirrors on both ends of an apparatus delivering an electrical current through the helium and neon gases. On December 13, Javan experiments by holding the first telephone conversation ever delivered by a laser beam. 1960 Continuously operating helium-neon gas laser invented Bell Laboratories researcher and former Townes student Ali Javan and his colleagues William Bennett, Jr., and Donald Herriott invent a continuously operating helium-neon gas laser. The continuous beam of laser light is extracted by placing parallel mirrors on both ends of an apparatus delivering an electrical current through the helium and neon gases. On December 13, Javan experiments by holding the first telephone conversation ever delivered by a laser beam. 1960 Operable laser invented Theodore Maiman, a physicist and electrical engineer at Hughes Research Laboratories, invents an operable laser using a synthetic pink ruby crystal as the medium. Encased in a "flash tube" and book ended by mirrors, the laser successfully produces a pulse of light. Prior to Maiman’s working model, Columbia University doctoral student Gordon Gould also designs a laser, but his patent application is initially denied. Gould finally wins patent recognition nearly 30 years later. 1961 Glass fiber demonstration Industry researchers Elias Snitzer and Will Hicks demonstrate a laser beam directed through a thin glass fiber. The fiber’s core is small enough that the light follows a single path, but most scientists still consider fibers unsuitable for communications because of the high loss of light across long distances. 1961 First medical use of the ruby laser In the first medical use of the ruby laser, Charles Campbell of the Institute of Ophthalmology at Columbia- Presbyterian Medical Center and Charles Koester of the American Optical Corporation use a prototype ruby laser photocoagulator to destroy a human patient’s retinal tumor.
1962 Gallium arsenide laser developed Three groups—at General Electric, IBM, and MIT’s Lincoln Laboratory—simultaneously develop a gallium arsenide laser that converts electrical energy directly into infrared light and that much later is used in CD and DVD players as well as computer laser printers. 1962 Gallium arsenide laser developed Three groups—at General Electric, IBM, and MIT’s Lincoln Laboratory—simultaneously develop a gallium arsenide laser that converts electrical energy directly into infrared light and that much later is used in CD and DVD players as well as computer laser printers.
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