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Niels Bohr Institute > Who, What, When > > Physics Spinoffs > Laser

08 June 2010

 

LASER

Powerful laser beams were adventurous fantasy for science fiction writers and for physicists, it was an exciting experiment. Nobody thought that they could be used for something practical. But today laser beams are used throughout society.

Aleksei Konstantinovitj Tolstoj (5. september 1817 -10. oktober 1875).

The idea that you that you could produce a beam of light so powerful that it could cut through metal, is old. For example, Aleksei Tolstoj wrote already in 1927 the science fiction novel "The Garin Death Ray". Here a scientist concentrates light beams between two mirrors until they become so powerful that they can destroy the enemy's ships on the horizon.

Ten years earlier, in 1917, Einstein had published the article "On the Quantum Theory of Radiation". Here he predicted that under certain circumstances an atom could be stimulated to emit light. In 1939, V.A. Fabrikant realized that this effect could produce a wave of light with the exact same direction and wavelength. In this way you could create a very powerful and narrow beam.

The idea of a powerful beam of light that could be aimed with great precision was fascinating for physicists. Even though no one could see the purpose of such a device, there were many who tried to produce it. From time to time small advances were made. In 1953, the physicist Townes succeeded in producing a device, which amplified microwaves - that is, waves of invisible light.


Theodore Harold "Ted" Maiman (juli 11, 1927 – maj 5, 2007) invented the first laser.

Invention of the first laser

But no one had succeeded in producing a machine with visible light beams. More and more researchers began to work on the case. It was a close race, but in 1960 Theodore H. Maiman succeeded. He was the first to present a working laser. It was constructed around a ruby crystal and emitted a red beam.

Initially, the laser was simply and interesting experiment. No one had thought to use it for anything practical. But today we use lasers everywhere in society.

For example, the scanner in the supermarket works by using a laser, CD and DVD players contain tiny lasers of crystal, physicists measure distances with lasers and fiber optic cables transmit signals from laser diodes.

One of the reasons that lasers are so useful is that they emit all of their light on a very small area. This area can become very hot. As a result, you can use the laser when it comes to welding tiny electrical connections together in computers or perform complex eye operations. And just as Tolstoj predicted in 1927, lasers can cut through metal. The large CO2-lasers are very powerful and are used in factories to cut iron and steel plates.

Gordon Gould (July 17, 1920 – September 16, 2005)

Why is it called a Laser

"Laser" is an acronym for "Light Amplification by Stimulated Emission of Radiation".

Gordon Gould, who created the word "laser", suggested that the first letter could be switched when naming devices that amplified other wavelengths than visible light. For example "xaser" for 'x-ray'-devices and "uvaser" for uv-devices.

The machine, which Townes invented in 1953, was actually called a "maser". But the other names never really became popular.

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