Not until 1954 did he and fellow researchers at Columbia prove it could be done. Using an electric field to direct excited molecules of ammonia gas into a thumb-sized copper chamber, they managed to get a sustained output of the desired radio waves. The device was given the name maser, for microwave amplification by stimulated emission of radiation, and it proved valuable for spectroscopy, the strengthening of extremely faint radio signals, and a few other purposes. But Townes would soon create a far bigger stir, teaming up with his physicist brother-in-law Arthur Schawlow to show how stimulated emission might be achieved with photons at the much shorter wavelengths of light—hence the name laser, with the "m" giving way to "l." In a landmark paper published in 1958 they explained that light could be reflected back and forth in the energized medium by means of two parallel mirrors, one of them only partly reflective so that the built-up light energy could ultimately escape. Six years later Townes received a Nobel Prize for his work, sharing it with a pair of Soviet scientists, Aleksandr Prochorov and Nikolai Gennadievich Basov, who had independently covered some of the same ground. Not until 1954 did he and fellow researchers at Columbia prove it could be done. Using an electric field to direct excited molecules of ammonia gas into a thumb-sized copper chamber, they managed to get a sustained output of the desired radio waves. The device was given the name maser, for microwave amplification by stimulated emission of radiation, and it proved valuable for spectroscopy, the strengthening of extremely faint radio signals, and a few other purposes. But Townes would soon create a far bigger stir, teaming up with his physicist brother-in-law Arthur Schawlow to show how stimulated emission might be achieved with photons at the much shorter wavelengths of light—hence the name laser, with the "m" giving way to "l." In a landmark paper published in 1958 they explained that light could be reflected back and forth in the energized medium by means of two parallel mirrors, one of them only partly reflective so that the built-up light energy could ultimately escape. Six years later Townes received a Nobel Prize for his work, sharing it with a pair of Soviet scientists, Aleksandr Prochorov and Nikolai Gennadievich Basov, who had independently covered some of the same ground. The first functioning laser—a synthetic ruby crystal that emitted red light—was built in 1960 by Theodore Maiman, an electrical engineer and physicist at the Hughes Research Laboratories. That epochal event set off a kind of evolutionary explosion. Over the next few decades lasers would take forms as big as a house and as small as a grain of sand. Along with ruby, numerous other solids were put to work as a medium for laser excitation. Various gases proved viable too, as did certain dye-infused liquids and some of the electrically ambivalent materials known as semiconductors. Researchers also developed many ways to excite a laser medium into action, pumping in the necessary energy with flash lamps, other lasers, electricity, and even chemical reactions. As for the laser light itself, it soon came in a broad range of wavelengths, from infrared to ultraviolet, with the output delivered as either pulses or continuous beams. All laser light has the same highly organized nature, however. In the language of science, it is practically monochromatic (of essentially the same wavelength), coherent (the crests and troughs of the waves perfectly in step, thus combining their energy), and highly directional. The result is an extremely narrow and powerful beam, far less inclined to spread and weaken than a beam of ordinary light, which is composed of a jumble of wavelengths out of step with one another.
Lasers have found applications almost beyond number. In manufacturing, infrared carbon dioxide lasers cut and heat-treat metal, trim computer chips, drill tiny holes in tough ceramics, silently slice through textiles, and pierce the openings in baby bottle nipples. In construction the narrow, straight beams of lasers guide the laying of pipelines, drilling of tunnels, grading of land, and alignment of buildings. In medicine, detached retinas are spot-welded back in place with an argon laser's green light, which passes harmlessly through the central part of the eye but is absorbed by the blood-rich tissue at the back. Medical lasers are also used to make surgical incisions while simultaneously cauterizing blood vessels to minimize bleeding, and they allow doctors to perform exquisitely precise surgery on the brain and inner ear. Lasers have found applications almost beyond number. In manufacturing, infrared carbon dioxide lasers cut and heat-treat metal, trim computer chips, drill tiny holes in tough ceramics, silently slice through textiles, and pierce the openings in baby bottle nipples. In construction the narrow, straight beams of lasers guide the laying of pipelines, drilling of tunnels, grading of land, and alignment of buildings. In medicine, detached retinas are spot-welded back in place with an argon laser's green light, which passes harmlessly through the central part of the eye but is absorbed by the blood-rich tissue at the back. Medical lasers are also used to make surgical incisions while simultaneously cauterizing blood vessels to minimize bleeding, and they allow doctors to perform exquisitely precise surgery on the brain and inner ear. Many everyday devices have lasers at their hearts. A CD or DVD player, for example, reads the digital contents of a rapidly spinning disc by bouncing laser light off minuscule irregularities stamped onto the disc's surface. Barcode scanners in supermarkets play a laser beam over a printed pattern of lines and spaces to extract price information and keep track of inventory. Pulsed lasers are no less versatile than their continuous-beam brethren. They can function like optical radar, picking up reflections from objects as small as air molecules, enabling meteorologists to detect wind direction or measure air density. The reflections can also be timed to measure distances—in some cases, very great indeed. A high-powered pulsed laser, aimed at mirrors that astronauts placed on the lunar surface, was used to determine the distance from Earth to the Moon to within 2 inches. The pulses of some lasers are so brief—a few quadrillionths of a second—that they can visually freeze the lightning-fast movements of molecules in a chemical reaction. And superpowerful laser pulses may someday serve as the trigger for controlled fusion, the long-sought thermonuclear process that could provide humankind with almost boundless energy.
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