Editing Laser (section)

=== Maser ===
{{Main|Maser}}

[[File:Aleksandr Prokhorov.jpg|thumb|right|[[Aleksandr Mikhailovich Prokhorov|Aleksandr Prokhorov]]]]

In 1951, [[Joseph Weber]] submitted a paper on using stimulated emissions to make a microwave amplifier to the June 1952 Institute of Radio Engineers Vacuum Tube Research Conference in [[Ottawa]], Ontario, Canada.<ref>{{cite web| url=https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4941| title=American Institute of Physics Oral History Interview with Joseph Weber| date=2015-05-04| access-date=March 16, 2016| archive-date=March 8, 2016| archive-url=https://web.archive.org/web/20160308061348/https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4941 |url-status=live}}</ref> After this presentation, [[RCA]] asked Weber to give a seminar on this idea, and [[Charles&nbsp;H. Townes]] asked him for a copy of the paper.<ref>{{cite book |last=Bertolotti |first=Mario |year=2015 |title=Masers and Lasers: An Historical Approach |publisher=CRC Press |pages=89–91 |isbn=978-1-4822-1780-3 |edition=2nd |url=https://books.google.com/books?id=4i_OBgAAQBAJ |access-date=March 15, 2016}}</ref>

[[File:Charles Townes.jpg|thumb|right|[[Charles H. Townes]]]]

In 1953, Charles H. Townes and graduate students [[James&nbsp;P. Gordon]] and [[Herbert&nbsp;J. Zeiger]] produced the first microwave amplifier, a device operating on similar principles to the laser, but amplifying [[microwave]] radiation rather than infrared or visible radiation. Townes's maser was incapable of continuous output.<ref>{{cite web |url=https://hobarts.com/guide-to-lasers |title=Guide to Lasers |website=Hobarts |access-date=24 April 2017 |archive-date=April 24, 2019 |archive-url=https://web.archive.org/web/20190424211422/https://hobarts.com/guide-to-lasers |url-status=live}}</ref> Meanwhile, in the Soviet Union, [[Nikolay Basov]] and [[Aleksandr Mikhailovich Prokhorov|Aleksandr Prokhorov]] were independently working on the [[Quantum harmonic oscillator|quantum oscillator]] and solved the problem of continuous-output systems by using more than two energy levels. These gain media could release [[stimulated emission]]s between an excited state and a lower excited state, not the ground state, facilitating the maintenance of a [[population inversion]]. In 1955, Prokhorov and Basov suggested optical pumping of a multi-level system as a method for obtaining the population inversion, later a main method of laser pumping.

Townes reports that several eminent physicists{{mdash}}among them [[Niels Bohr]], [[John von Neumann]], and [[Llewellyn Thomas]]{{mdash}}argued the maser violated Heisenberg's [[uncertainty principle]] and hence could not work. Others such as [[Isidor Rabi]] and [[Polykarp Kusch]] expected that it would be impractical and not worth the effort.<ref>Townes, Charles H. (1999). [https://books.google.com/books?id=VrbD41GGeJYC&dq=%22niels+bohr%22+rabi+kusch+von+neumann+laser&pg=PA69 ''How the Laser Happened: Adventures of a Scientist''], [[Oxford University Press]], {{ISBN|978-0-19-512268-8}}, pp. 69–70.</ref> In 1964, Charles H. Townes, Nikolay Basov, and Aleksandr Prokhorov shared the [[Nobel Prize in Physics]], "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser–laser principle".