Editing Laser (section)

=== Foundations ===

In 1917, [[Albert Einstein]] established the theoretical foundations for the laser and the [[maser]] in the paper "''Zur Quantentheorie der Strahlung''" ("On the Quantum Theory of Radiation") via a re-derivation of [[Max Planck]]'s law of radiation, conceptually based upon probability coefficients ([[Einstein coefficients]]) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation.<ref name=Einstein1917>{{cite journal |last=Einstein |first=A |title=Zur Quantentheorie der Strahlung |journal=Physikalische Zeitschrift |year=1917 |volume=18 |pages=121–128 |bibcode = 1917PhyZ...18..121E }}</ref> In 1928, [[Rudolf W. Ladenburg]] confirmed the existence of the phenomena of stimulated emission and negative absorption.<ref>{{Cite book |last1=Steen |first1=W. M. |url=https://books.google.com/books?id=gPsq0HHAU4UC&pg=PA11 |title=Laser Material Processing |last2=Steen |first2=William M. |last3=Mazumder |first3=J. |date=2010 |publisher=Springer |isbn=978-1-84996-062-5 |edition=4th |location= |pages=5, 11}}</ref> In 1939, [[Valentin A. Fabrikant]] predicted using stimulated emission to amplify "short" waves.<ref>{{cite web |url=http://wwwold.unimib.it/ateneo/presentazione/direzione_ammva/prevenzione_protezione/Semin_sicur_laser.ppt |title=Il rischio da laser: cosa è e come affrontarlo; analisi di un problema non così lontano da noi |trans-title=The risk from laser: what it is and what it is like facing it; analysis of a problem which is thus not far away from us |series=Programma Corso di Formazione Obbligatorio |year=2004 |first=Dimitri |last=Batani |format=Powerpoint |access-date=January 1, 2007 |website=wwwold.unimib.it |publisher=University of Milano-Bicocca |language=it |archive-url=https://web.archive.org/web/20070614115935/http://wwwold.unimib.it/ateneo/presentazione/direzione_ammva/prevenzione_protezione/Semin_sicur_laser.ppt |archive-date=June 14, 2007 |page=12}}</ref> In 1947, [[Willis&nbsp;E. Lamb]] and R.{{nbsp}}C.{{nbsp}}Retherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission.<ref>{{Cite book |last1=Steen |first1=W. M. |url=https://books.google.com/books?id=gPsq0HHAU4UC&pg=PA5 |title=Laser Material Processing |last2=Steen |first2=William M. |last3=Mazumder |first3=J. |date=2010 |publisher=Springer |isbn=978-1-84996-062-5 |edition=4th |location= |pages=5}}</ref> In 1950, [[Alfred Kastler]] (Nobel Prize for Physics 1966) proposed the method of [[optical pumping]], which was experimentally demonstrated two years later by Brossel, Kastler, and Winter.<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1966/press.html The Nobel Prize in Physics 1966] {{Webarchive |url=https://web.archive.org/web/20110604225702/http://nobelprize.org/nobel_prizes/physics/laureates/1966/press.html |date=June 4, 2011 }} Presentation Speech by Professor Ivar Waller. Retrieved January 1, 2007.</ref>