Editing Nonlinear optics (section)

===Related processes===
In these processes, the medium has a linear response to the light, but the properties of the medium are affected by other causes:
* [[Pockels effect]], the refractive index is affected by a static electric field; used in [[electro-optic modulator]]s.
* [[Acousto-optics]], the refractive index is affected by acoustic waves (ultrasound); used in [[acousto-optic modulator]]s.
* [[Raman scattering]], interaction of photons with optical [[phonon]]s.