Who Invented the Laser?
Physicists had been working for generations toward controlling ever shorter wavelengths. After radio (meters) and radar (centimeters, then millimeters), the logical next step would be far-infrared waves. Masers had been modestly useful, more for scientific research than for military or industrial applications. Only a few scientists thought an infrared maser might be important and pondered how to make one. Infrared rays could not be manipulated like radar, and indeed were hard to manage at all.
Townes thought about the problems intensively. One day in 1957, studying the equations for amplifying radiation, he realized that it would be easier to make it happen with very short waves than with far-infrared waves. He could leap across the far-infrared region to the long-familiar techniques for manipulating ordinary light. Townes talked it over with his colleague, friend and brother-in-law Arthur Schawlow.
Schawlow found the key — put the atoms you wanted to stimulate in a long, narrow cavity with mirrors at each end. The rays would shuttle back and forth inside so that there would be more chances for stimulating atoms to radiate. One of the mirrors would be only partly silvered so that some of the rays could leak out. This arrangement (the Fabry-Pérot etalon) was familiar to generations of optics researchers.
The same arrangement meanwhile occurred to Gordon Gould, a graduate student at Columbia University who had discussed the problem with Townes. For his thesis research, Gould had already been working with "pumping" atoms to higher energy states so they would emit light. As Gould elaborated his ideas and speculated about all the things you could do with a concentrated beam of light, he realized that he was onto something far beyond the much-discussed "infrared maser". In his notebook he confidently named the yet-to-be-invented device a LASER (for Light Amplification by Stimulated Emission of Radiation).
Gould, Schawlow and Townes now understood how to build a laser — in principle. To actually build one would require more ideas and a lot of work. Some of the ideas were already in hand. Other physicists in several countries, aiming to build better masers, had worked out various ingenious schemes to pump energy into atoms and molecules in gases and solid crystals. In a way they too were inventors of the laser. So were many others clear back to Einstein.
In 1957 Townes talked over some ideas about pumping light-energy into atoms with Gordon Gould, a graduate student who had been thinking along similar lines. Worried that he might be scooped, Gould wrote down his ideas for the record. He developed many more ideas of how lasers could be built and used, and in April 1959 he filed patent applications with his employer, the high-tech research firm TRG. Nine months earlier Schawlow and Townes had applied for a patent on behalf of Bell Laboratories, which employed Schawlow on staff and Townes as a consultant.
When the Bell patent was granted, Gould sued, claiming he was first to conceive the device. Legal battles raged for the next thirty years. If Gould’s patents were valid, everyone who built or used a laser would owe him money—and the longer the patents were undecided, the more valuable they became as the laser industry grew. In 1987 Gould and his backers began to win settlements. One of the greatest patent wars in history was over.
The historical question of how to assign credit for inventing the laser remains controversial. Most of the ideas were patented by someone, but that tells little about how the ideas actually arose and spread among scientists.