Nonlinear optics

Summary

Nonlinear optics studies light in media whose polarization density depends nonlinearly on the electric field of the light. The effects appear at high intensities, in practice with lasers. They include the generation of new frequencies, such as second-harmonic generation, and an intensity-dependent refractive index, the optical Kerr effect. Its mathematical models are nonlinear wave equations, such as the nonlinear Schrödinger equation.