Nonlinear optics

Nonlinear optics is a branch of optics describing phenomena that occur at high light intensities, when a material's polarization (its response to an electric field) stops being directly proportional to the field's intensity.

What phenomena does nonlinear optics cover?

Typical nonlinear effects include second-harmonic generation (doubling the frequency of light), the Kerr effect (a change in refractive index proportional to light intensity), four-wave mixing, and self-phase modulation — phenomena that matter at high power in lasers and long-haul transmission systems.

Applications

Nonlinear phenomena are deliberately exploited in tunable lasers and frequency generators, but they also pose a limitation in high-power DWDM transmission systems — fiber nonlinearity (the Kerr effect) introduces crosstalk between channels and degrades signal quality over long routes.

Related terms

Chromatic dispersion

FDTD

BPM