Editing Nonlinear optics (section)

===Other nonlinear processes===
* Optical [[Kerr effect]], intensity-dependent refractive index (a <math>\chi^{(3)}</math> effect).
* [[Self-focusing]], an effect due to the optical [[Kerr effect]] (and possibly higher-order nonlinearities) caused by the [[Spatial mode|spatial variation in the intensity]] creating a spatial variation in the refractive index.
* [[Kerr-lens modelocking]] (KLM), the use of [[self-focusing]] as a mechanism to [[Mode-locking|mode-lock]] laser.
* [[Self-phase modulation]] (SPM), an effect due to the optical [[Kerr effect]] (and possibly higher-order nonlinearities) caused by the [[Wavepacket|temporal variation in the intensity]] creating a temporal variation in the refractive index.
* [[Soliton (optics)|Optical solitons]], an equilibrium solution for either an [[Optical pulses|optical pulse]] (temporal soliton) or [[spatial mode]] (spatial soliton) that does not change during propagation due to a balance between [[dispersion (optics)|dispersion]] and the [[Kerr effect]] (e.g. [[self-phase modulation]] for temporal and [[self-focusing]] for spatial solitons).
* Self-diffraction, splitting of beams in a multi-wave mixing process with potential energy transfer.<ref>{{Cite journal|last1=Hernández-Acosta|first1=M A|last2=Soto-Ruvalcaba|first2=L|last3=Martínez-González|first3=C L|last4=Trejo-Valdez|first4=M|last5=Torres-Torres|first5=C|date=2019-09-17|title=Optical phase-change in plasmonic nanoparticles by a two-wave mixing|url=https://doi.org/10.1088/1402-4896/ab3ae9|journal=Physica Scripta|volume=94|issue=12|pages=125802|doi=10.1088/1402-4896/ab3ae9|bibcode=2019PhyS...94l5802H|s2cid=202145209|issn=0031-8949}}</ref>
* [[Cross-phase modulation]] (XPM), where one wavelength of light can affect the phase of another wavelength of light through the optical Kerr effect.
* [[Four-wave mixing]] (FWM), can also arise from other nonlinearities.
* [[Cross-polarized wave generation]] (XPW), a <math>\chi^{(3)}</math> effect in which a wave with polarization vector perpendicular to the input one is generated.
* [[Modulational instability]].<ref name="Zakharov 540–548">{{Cite journal|last1=Zakharov|first1=V. E.|last2=Ostrovsky|first2=L. A.|date=2009-03-15|title=Modulation instability: The beginning|journal=Physica D: Nonlinear Phenomena|volume=238|issue=5|pages=540–548|doi=10.1016/j.physd.2008.12.002|bibcode=2009PhyD..238..540Z}}</ref>
* [[Raman amplification]]<ref>{{cite journal |first1=A.P. |last1=Kouzov |first2=N.I. |last2=Egorova |first3=M. |last3=Chrysos |first4=F. |last4=Rachet |title=Non-linear optical channels of the polarizability induction in a pair of interacting molecules |journal=Nanosystems: Physics, Chemistry, Mathematics |volume=3 |issue=2 |page=55 |date=2012 |url=http://nanojournal.ifmo.ru/en/articles-2/volume3/3-2/physics/paper05/ |access-date=2015-10-31 |archive-date=2017-06-13 |archive-url=https://web.archive.org/web/20170613130115/http://nanojournal.ifmo.ru/en/articles-2/volume3/3-2/physics/paper05/ |url-status=live }}</ref>
* [[Optical phase conjugation]].
* [[Brillouin scattering#Stimulated Brillouin scattering|Stimulated Brillouin scattering]], interaction of photons with acoustic phonons
* [[Two-photon absorption|Multi-photon absorption]], simultaneous absorption of two or more photons, transferring the [[energy]] to a single electron.
* Multiple [[photoionisation]], near-simultaneous removal of many bound electrons by one photon.
* [[Optical chaos|Chaos in optical systems]].