The Invention of the Laser
The concept of a laser – a concentrated beam of light – seems obvious today. It is the same one that runs through a child’s mind when she points a magnifying glass at an ant. But, the seeming simplicity of a light beam, and the fact that it now fits on the end of a pen, masks the much more complicated physical process behind it. The discovery of that process was an enormous breakthrough in physics; a breakthrough that has given us DVD players, laser printers, eye surgery, and, undoubtedly, a host of things to come.
The principles behind the laser came from a theory of Einstein’s, but its story, like many other post-war inventions, began with the military. In 1948, the Pentagon provided Columbia University with the funds to hire a new team of physicists and directed them to work on microwave radar technology. One of the physicists hired was Charles Townes. Three years later, Townes completed work on what he called a maser (Microwave Amplification by the Stimulated Emission of Radiation).
As the name implies, the physics behind the maser and laser were basically the same. Einstein’s theory predicted that when certain types of atoms came in contact with enough radiation (microwaves, light, etc.) of the right wavelength, the radiation would stimulate the emission of more radiation of the exact same wavelength, essentially doubling the power of the wave. That extra radiation would then stimulate more, producing an increasingly powerful and coherent signal.
The maser was the first device to take this theory of physics and put it to practical use, and it later won Townes a Nobel Prize. But its uses were limited, and the real prize, Townes quickly realized, was a device to amplify and concentrate radiation at a much higher frequency – visible light. Higher frequencies, however, required supplying and harnessing higher levels of energy, and it took several years of work, funded by the Air Force Office of Scientific Research, before he made his breakthrough.
Although he did not know it, Townes was not the only one working toward the laser. During a conversation with Townes, one of his graduate students, Gordon Gould, picked up the idea of an optical maser and began to work on it in his spare time. That work eventually replaced his thesis research, and Columbia and Townes both dismissed him as an unfocused physicist who would never make it. So, Gould took his research to the Technical Research Group, a small military contractor in Manhattan, and together, they applied for funding to build the first laser.
After many rejections, they finally took their proposal to the Pentagon’s Advanced Research Projects Agency (DARPA), a government department designed to encourage long-term research with potentially large payoffs. DARPA seized upon the idea and provided TRG with four times the funding it requested, enough money to hire four teams to work on separate prototypes. On December 15, 1958, Gould submitted a patent application that sketched out the principles behind the laser, the same principles that appeared, unknown to Gould, in a paper published a day earlier by Charles Townes.
With the idea of the laser out in the open, many others joined the race to actually build it. Bell Labs put three teams on it, and with the resources from AT&T’s telephone monopoly, were considered the favorites. But both Bell and Columbia took the wrong tack. Following Townes’s paper, most people assumed that the easiest material to stimulate was a gas, and that solids, with their more complicated internal structure, would prove too difficult.
Gould and ARPA did not make this mistake, but they did run into a bureaucratic complication that ended their chances. DARPA and the research wing of the government believed in Gould and the laser, but this was shortly after the McCarthy era, and the security wing still held a great deal of power. A check into Gould’s background revealed decades old activity in leftist groups, and over DARPA’s strong objections, he was not allowed to work on his own project.
With these groups struggling, another military contractor, Howard Hughes’s Hughes Research Laboratories, entered the mix, this time with a contract from the Army Signal Corps. The contract called for further research into microwave masers, but it allowed Hughes Labs to hire Ted Maiman and put him to work on an optical maser. Like everyone else, Maiman had read Townes’s paper, but he was not convinced that a solid-state laser would not work. In fact, because of his background in engineering, Maiman insisted on working with a solid. If it worked, he argued, it would produce a much more practical laser than the finicky gas version.
Finally, on May 16, 1960, Maiman built the first laser (Light Amplification by the Stimulated Emission of Radiation). He began with a synthetic ruby rod, coated the ends with silver (leaving a small hole in one end for the beam to come out), and placed the rod inside an ordinary photo flash lamp. When he turned the flash on, it excited the atoms inside the ruby, causing them to glow. The light waves from the glow stimulated other atoms in the ruby to emit more light waves, which bounced around inside the rod until they built up enough power to emerge through the hole as a coherent, ruby-red light beam. The government had backed several more likely candidates, but in the end, Ted Maiman gave it, and us, the laser.
Bromberg, Joan Lisa. The Laser in America, 1950-1970. Cambridge, MA: MIT Press, 1991.
Hecht, Jeff. Beam: The Race to Make the Laser. New York: Oxford University Press, 2005.