Radar, Rubies and Razors: How the Laser Learned to Shine
06/08/2015 - Oliver Hagenlocher
When Charles Hard Townes died in January 2015 there were no outpourings of grief in the media. Yet Townes, together with Nikolay Gennadiyevich Basov and Aleksandr Mikhailovich Prokhorov, won the Nobel Prize for an invention in 1964, without which the world would be a very different place today. Films on DVD or Blu-ray and music on CDs would not be possible without the fantastic invention which was actually designed to improve the power of microwave radiation.
Townes began his career at Bell Labs, where he was involved with the development of radar systems driven mainly by the Second World War, as he was able to provide knowledge from the microwave research he conducted before the war. After the war, Townes continued his research into microwave spectroscopy, but like his colleagues with whom he later shared the Nobel Prize, he hit a technological barrier impossible to overcome at the time. In an attempt to build a microwave amplifier for the shortest possible wavelengths, the 3 Nobel Prize winners failed due to the technology available to them and were forced to move in a different direction, at which point they returned to a theory postulated by Einstein.
The maser – forerunner of the laser
Einstein predicted that electromagnetic radiation interacts with matter, a process which has not been proven to date. Einstein named the process “stimulated emission.” To understand this process in its entirety, one needs an understanding of quantum physics, which is why we will attempt to provide a simplified version here. Atoms are always in a quantized energy state and this can be converted into an excited state by adding energy. If the atom returns to its initial state, the energy previously added to it will be discharged in the form of photons. This can then be used to amplify radiation.
Since it was not technically possible to produce a microwave amplifier for short wavelengths, Townes, Basov and Prokhorov had the idea of using this effect to amplify short wavelengths. This was the idea that gave rise to the maser. After two years of intensive research, Townes and his working group finally managed to produce the first working maser in 1953, which confirmed Einstein's theory making it possible to amplify microwaves by stimulated emission using radiation.
Further in the spectrum
The development of the maser to produce the laser was ultimately the next logical step in the development of the principle, since smaller and smaller wave bands were used until they finally came to the optical wavelength spectrum. In 1958, Townes and Arthur Leonard Schawlow unveiled the concept of the laser to the public and applied for a patent. However, a further two years were to pass before the first functional laser was produced, astonishingly not by Townes and his group, but by Thomas Maiman, who worked at the Hughes Aircraft laboratories. This first laser was a solid laser based on a ruby. To be fair, we must say that the design for the laser came from Townes and his team, but it was Maiman who managed to make the whole thing work. Radars and rubies, so far so good, but where do razor blades come into the picture? The answer is as simple as it is curious. Since they had created a whole new field of technology, there was simply no unit to describe the power of a laser. Since, however, they were experimenting with the power of the laser beam by shooting them at Gillette razor blades to measure how many the laser would pass through, Gillette was the initial unit used to declare this power.
An invention with thousands of applications
Since the development of the laser almost 60 years ago, a wide range of technical applications have been developed on the basis of the laser. The optical media as we know it today would be inconceivable without the laser, as would lots of technical processes in modern manufacturing, such as laser marking and laser welding. With the latter, EMAG, after many years of working with gas lasers such as CO2, currently uses solid state lasers – the same principle used for the first laser. As it turns out, the use of solid state lasers in modern production laser welding systems reduces costs drastically. Not only is less energy required to power the source, but the entire design of a laser welding system using a solid state laser only takes up a fraction of the space required by a comparable system with a CO2 laser, as the gas systems are not required. The ELC series laser welding systems are primarily used in the production of gearbox elements and also make it possible to manufacture lightweight components. Who would have thought that the lightweight construction of gearbox components for vehicles started with the development of radar systems and microwave amplifiers?