A laser is essentially a beam of coherent light. This means that it does not scatter quickly like the light that comes out of a flashlight, but rather it stays forming a beam over long distances , and it is also monochromatic : while the light from a light bulb emits in the entire range of visible light, a laser beam is confined to a very small part of the spectrum.
The prehistory of the laser must be placed when Albert Einstein writes the third of the articles on the way in which matter interacts with light. Published in 1917, it was entitled ” On the Quantum Theory of Radiation” , and there he described the theory of stimulated emission of radiation. To understand it, we must understand how an atom emits light : if one of its electrons absorbs a photon of light with the right energy, it rises to a higher energy level; he is said to be excited. After a while, it falls to a lower energy level, emitting a photon whose energy is exactly the one that separates those two levels. This is spontaneous emission. The stimulated emission is that if we have an electron in a higher level and we send a photon with the same energy as the difference between the levels, the electron will fall to the lower level emitting a photon with the same energy as the incident photon. Obviously, if we have a whole population of electrons excited at the same level, we can obtain a cascade of photons, all with the same energy : that is the laser. This was what Einstein had described. In 1928, Rudolf W. Ladenburg confirmed the existence of stimulated emission phenomena and in 1950 Alfred Kastler proposed an effective way of inverting the population of electrons, optical pumping, which was experimentally confirmed two years later.
On April 26, 1951 , Charles Hard Townes of Columbia University sat on a park bench in Washington, far from home. He’d had a meeting because the Pentagon, which was funding some of his work at the Radiation Laboratory, wanted to improve their communications and radar systems by using shorter wavelengths to reach greater distances. That spring morning in the park, Townes had an idea of how to build a device capable of stimulating the amplified emission of microwaves: the maser. Two years later , and together with two postgraduate students, James P. Gordon and HJ Zeiger, he finished building the first maser in history . And they patented their creation, which only amplified microwaves, not infrared or visible light.
Could they apply the maser principle to visible light? To see if it was possible, he teamed up with his brother-in-law, Arthur L. Schawlow , who worked at Bell Laboratories, the same company that paid Townes as a consultant. On weekdays Schawlow researched superconductivity—which was what he was paid for at Bell—and on weekends he hung out with his brother-in-law to see how they could build a visible-light maser. In December 1958 they published the results of their effort in the journal Physical Review, “Infrared and optical masers” and through Bell Laboratories they patented their idea.
But the story does not end here; this was the starting signal of a patent war that lasted 30 years .
To understand what happened, we must go back to 1957, when a Columbia University doctoral student, Gordon Gould , came up with a way to build an optical resonator , a fundamental piece without which it is impossible to obtain a narrow laser beam. consistent and intense. He had already done something similar in 1956 for Townes , when he proposed how to perform optical pumping for his maser. He described the resonator in his workbook – in addition to its other possible applications such as spectrometry, interferometry, radar and nuclear fusion – under the title “Rough calculations on the feasibility of a LASER: Light Amplification by Stimulated Emission of Radiation” : this is the first time the acronym laser appears. Gould knew what he had in his hands so he directed his steps to a notary so that, at least, his work was properly certified.
In 1959 he left Columbia University because he was eager to patent his invention and because he mistakenly believed that he had to build a laser in order to patent it. He abandoned his doctoral thesis and went to work in a private company, Technical Research Group (TRG). Gould convinced them to work on developing a laser, even securing funding from the Department of Defense research agency DARPA . But then things went awry: DARPA declared the project ‘classified’ and as Gould had been involved in ‘communist activities’, he was banned from the project. Without Gould TRG lost the race, which was won by the newly founded Hughes Research Laboratories, the research arm of Hughes Aircraft. Theodore Maiman operated the first laser on May 16, 1960 , shining a high-power flashlamp onto a rod of pink ruby with silver-coated surfaces. He immediately wrote an article recounting his work to the prestigious Physical Review Letters , but was surprisingly rejected . Maiman played it and sent it to Nature -a journal even more selective than PRL-; the editors accepted it and it was published on August 6. But his company was not going to wait for it to appear published and on July 7, 1960 he gave a press conference announcing the discovery. We can imagine the stir that raised, and began to speak of the “death ray.” ..
Gould had further refined his idea and filed a patent application in April 1959 . The United States Patent Office denied it because Bell Laboratories had filed its laser patent before him . At that time the criterion used for the granting of patents was the first to invent (the first to invent), unlike in Europe , where the rule of first to file (the first to ask for it) was (and is) followed. ). So Gould pulled out his 1957 notarized notebook and along with TRG went to court . This led to a very long litigation that lasted 28 years. In 1973 the United States Patent and Customs Court of Appeals ruled that the original patent issued to Schawlow and Townes was too general, not providing enough information to build certain key components, and in 1985 the Federal Court in Washington ordered the Patent Office that granted the patent to Gould.
