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No Laser Tag If Not for These Brilliant Pioneering Physicists

This article was contributed by Mark Sterrett, Research Analyst at Global Patent Solutions.


Previously, in this ten part series, we covered Guglielmo Marconi’s and Dr. Karl Ferdinand Braun’s wireless telegraphy device for which they won the Nobel Prize in physics. This week we are covering the intricate subject of quantum electronics, for which Charles Hard Townes, in association with Nicolay Gennadiyevich Basov and Aleksandr Mikhailovich Prokhorov, shared the Nobel Prize in 1964.

Known today more generally as solid state physics or semiconductor physics, quantum electronics deals with electronics which utilize the properties of electrons and photons to provide oscillations, absorption, and emission. More specifically, Townes and his associates focused on expanding a concept called stimulated emission which was introduced by physics giant Albert Einstein in 1917. Stimulated emission is the process in which an electron absorbs a frequency of radiation, thereby increasing its quantum energy level, and then re-emits the frequency of radiation upon reaching a lower energy state. At the time, stimulated emission was thought to be strictly theoretical because the absorption was orders of magnitude higher than amplification.

Townes and associates discovered a way to provide amplification that was orders in magnitude higher than the absorption using a concept called an inverted population. An inverted population is an unstable condition in which there are more atoms in a high energy state than in a lower energy state, thus providing more emission upon reaching a lower energy state. The device that Townes and associates created was called a M.A.S.E.R. (MASER), also known as, microwave amplification by stimulated emission of radiation. It is important to know that this MASER is the basis for the modern LASER which substitutes “microwave” for “light”.

US 2,879,439 A to Townes, C. discloses modestly the “Production of electromagnetic energy” which details the invention in full. Published March 24, 1959 Townes describes a system of oscillator elements which are normally in a stable, or equilibrium, state due to exchanges of energy between oscillates in a higher state of energy. Modern lasers are based on the concept of providing incident light into a gain medium, which may be a gas, which is provided into a resonator cavity defined by the distance between two opposing specially designed mirrors. Townes invention as described is quite similar, minus the mirrors, in which a focused beam of atoms is brought into a cavity in which microwave radiation is introduced. As shown in the patent’s figures, the atoms, which are at a higher energy state, drop to a lower energy state and provide a microwave output which is orders higher than the input; thus providing a working MASER.

The patent has only two independent claims which detail an apparatus for obtaining electromagnetic energy and a paramagnetic means providing an ensemble of molecules in energy equilibrium at two different energy states. It is referenced by twenty-two other patents, and it cites four previous patents. Finally, it is classified under the CPC as H01S 1/06: gaseous beam masers, which is a subclass for LASERS.

In our next blog entry in this series, we will be covering Leo Esaki’s quantum tunneling phenomena.

 

CITATIONS:

http://www.nobelprize.org/nobel_prizes/physics/laureates/1964/press.html

“Charles H. Townes – Facts”. Nobelprize.org. Nobel Media AB 2014. Web. 11 Aug 2014. http://www.nobelprize.org/nobel_prizes/physics/laureates/1964/townes-facts.html

“Nicolay G. Basov – Facts”. Nobelprize.org. Nobel Media AB 2014. Web. 11 Aug 2014. http://www.nobelprize.org/nobel_prizes/physics/laureates/1964/basov-facts.html

“Aleksandr M. Prokhorov – Facts”. Nobelprize.org. Nobel Media AB 2014. Web. 11 Aug 2014. http://www.nobelprize.org/nobel_prizes/physics/laureates/1964/prokhorov-facts.html

https://www.google.com/patents/US2929922?dq=US 2,929,922hl=ensa=Xei=GP_oU5njFs3goAS7q4GgBgved=0CBwQ6AEwAA

https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Stimulated_emission.html