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In 1956, Gould proposed using optical pumping to excite a maser, and discussed this idea with the maser's inventor Charles Townes, who was also a professor at Columbia and later won the 1964 Nobel prize for his work on the maser and the laser. Townes gave Gould advice on how to obtain a patent on his innovation, and agreed to act as a witness.


Invention of the laser

By 1957, many scientists including Townes were looking for a way to achieve maser-like amplification of visible light. In November of that year, Gould realized that one could make an appropriate optical resonator by using two mirrors in the form of a Fabry–Pérot interferometer. Unlike previously considered designs, this approach would produce a narrow, coherent, intense beam. Since the sides of the cavity did not need to be reflective, the gain medium could easily be optically pumped to achieve the necessary population inversion. Gould also considered pumping of the medium by atomic-level collisions, and anticipated many of the potential uses of such a device.

Gould recorded his analysis and suggested applications in a laboratory notebook under the heading "Some rough calculations on the feasibility of a LASER: Light Amplification by Stimulated Emission of Radiation"—the first recorded use of this acronym. Gould's notebook was the first written prescription for making a viable laser and, realizing what he had in hand, he took it to a neighborhood store to have his work notarized. Arthur Schawlow and Charles Townes independently discovered the importance of the Fabry–Pérot cavity—about three months later—and called the resulting proposed device an "optical maser". Gould's name for the device was first introduced to the public in a conference presentation in 1959, and was adopted despite resistance from Schawlow and his colleagues.


Battles for patents

During this time, Gould and TRG began applying for patents on the technologies Gould had developed. The first pair of applications, filed together in April 1959, covered lasers based on Fabry–Pérot optical resonators, as well as optical pumping, pumping by collisions in a gas discharge (as in helium-neon lasers), optical amplifiers, Q-switching, optical heterodyne detection, the use of Brewster's angle windows for polarization control, and applications including manufacturing, triggering chemical reactions, measuring distance, communications, and lidar. Schawlow and Townes had already applied for a patent on the laser, in July 1958. Their patent was granted on March 22, 1960. Gould and TRG launched a legal challenge based on his 1957 notebook as evidence that Gould had invented the laser prior to Schawlow and Townes's patent application. (At the time, the United States used a first to invent system for patents.) While this challenge was being fought in the Patent Office and the courts, further applications were filed on specific laser technologies by Bell Labs, Hughes Research Laboratories, Westinghouse, and others. Gould ultimately lost the battle for the U.S. patent on the laser itself, primarily on the grounds that his notebook did not explicitly say that the sidewalls of the laser medium were to be transparent, even though he planned to optically pump the gain medium through them, and considered loss of light through the sidewalls by diffraction.

Gould's first laser patent was awarded in 1968, covering an obscure application—generating X-rays using a laser. The technology was of little value, but the patent contained all the disclosures of his original 1959 application, which had previously been secret. This allowed the patent office greater leeway to reject patent applications that conflicted with Gould's pending patents. Meanwhile the patent hearings, court cases, and appeals on the most significant patent applications continued, with many other inventors attempting to claim precedence for various laser technologies. The question of just how to assign credit for inventing the laser remains unresolved by historians.


Further patent battles, and enforcement of issued patents

Gould was later involved in legal battles, as the laser industry sought to not only prevent the Patent Office from issuing Gould's remaining patents, but also to have the already-issued ones revoked. Gould and his company were forced to fight both in court, and in Patent Office review proceedings. According to Gould and his lawyers, the Office seemed determined to prevent Gould from obtaining any more patents, and to rescind the two that had been granted.

The delay—and the subsequent spread of lasers into many areas of technology—meant that the patents were much more valuable than if Gould had won initially. Even though Gould had signed away eighty percent of the proceeds in order to finance his court costs, he made several million dollars.

"I thought that he legitimately had a right to the notion to making a laser amplifier," said William R. Bennett, who was a member of the team that built the first laser that could fire continuously. "He was able to collect royalties from other people making lasers, including me."


Election to Hall of Fame and death

Even though his role in the actual invention of the laser was disputed over decades, Gould was elected to the National Inventors Hall of Fame in 1991.