Optical Kerr effect
= Optical Kerr effect
{title2=$n=n_0+n_2I$}
An intensity-dependent <refractive index> produced by the optical field itself. In a simple instantaneous isotropic model, $n=n_0+n_2I$. A transversely nonuniform <intensity> produces <self-focusing> for positive $n_2$ and <self-defocusing> for negative $n_2$. Temporal intensity variation produces <self-phase modulation>. These are consequences of a third-order <nonlinear optical susceptibility>, distinct from a static applied-field <electro-optic Kerr effect>.