Editing Nonlinear optics (section)

==History==
The first nonlinear optical effect to be predicted was [[two-photon absorption]], by [[Maria Goeppert Mayer]] for her PhD in 1931, but it remained an unexplored theoretical curiosity until 1961 and the almost simultaneous observation of two-photon absorption at [[Bell Labs]]<ref>{{Cite journal|doi=10.1103/PhysRevLett.7.229|bibcode=1961PhRvL...7..229K |title=Two-Photon Excitation in CaF2:Eu2+|journal=Physical Review Letters|volume=7|issue=6|pages=229|year=1961|last1=Kaiser |first1=W.|last2=Garrett|first2=C. G. B.}}</ref>
and  the discovery  of  [[second-harmonic generation]] by [[Peter Franken]] ''et al.'' at [[University of Michigan]], both shortly after the construction of the first laser by [[Theodore Maiman]].<ref name=Rigamonti2010>{{Cite journal|first= Luca|last= Rigamonti|title= Schiff base metal complexes for second order nonlinear optics|journal= La Chimica & l'Industria|url= http://www.soc.chim.it/sites/default/files/chimind/pdf/2010_3_118_ca.pdf|issue= 3|date= April 2010|pages= 118–122|access-date= 2015-10-21|archive-url= https://web.archive.org/web/20160101090430/http://www.soc.chim.it/sites/default/files/chimind/pdf/2010_3_118_ca.pdf|archive-date= 2016-01-01|url-status= dead}}</ref> However, some nonlinear effects were discovered before the development of the laser.<ref>{{cite journal|last1=Lewis|first1=Gilbert N.|last2=Lipkin|first2=David|last3=Magel|first3=Theodore T.|title=Reversible Photochemical Processes in Rigid Media. A Study of the Phosphorescent State|journal=Journal of the American Chemical Society|date=November 1941|volume=63|issue=11|pages=3005–3018|doi=10.1021/ja01856a043|language=EN}}</ref> The theoretical basis for many nonlinear processes was first described in [[Nicolaas Bloembergen|Bloembergen]]'s monograph "Nonlinear Optics".<ref>{{Cite book|title=Nonlinear Optics|last=Bloembergen|first=Nicolaas|year=1965|publisher=World Scientific |isbn=978-9810225995}}</ref>