# What is nonlinear optical coefficient?

## What is nonlinear optical coefficient?

Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization density P responds non-linearly to the electric field E of the light.

### What is a nonlinear coefficient?

Such a nonlinear coefficient (which can also be called SPM coefficient) occurs e.g. in the nonlinear Schrödinger equation for the evolution of ultrashort pulses in a fiber. Its units are rad / (W m) (radians per Watt and meter). From it, one can calculate the nonlinear length.

#### Why do nonlinear optical effects occur?

What are nonlinear-optical effects and why do they occur? Sending infrared light into a crystal yielded this display of green light: Nonlinear optics allows us to change the color of a light beam, to change its shape in space and time, and to create the shortest events ever made by humans.

**How do you calculate nonlinear refractive index?**

Now the nonlinear refractive index n2 can be calculated from the nonlinear susceptibility by n2 = (12π/n0) χ 1111 ( 3 ) (–ω; ω, ω, –ω), were n0 is the linear refractive index of the material.

**Can nonlinearity be negative?**

The nonlinearity can also be negative (self-defocusing nonlinearity), particularly for photon energies above ≈ 70% of the bandgap energy. Materials with a high nonlinear index often have a small bandgap energy, and therefore also often exhibit strong two-photon absorption (TPA).

## What is the meaning of the effective nonlinear coefficient?

Effective Nonlinear Coefficient. Definition: a coefficient for quantifying the strength of a nonlinear interaction. German: effektiver nichtlinearer Koeffizient. Category: nonlinear optics. How to cite the article; suggest additional literature.

### How to calculate the effective nonlinearity of a material?

The effective nonlinearity can then relatively simply be calculated from the nonlinear tensor of the material.

#### How is the strength of a nonlinear interaction determined?

Since the strength of such nonlinear interactions usually depends not only on the effective nonlinear coefficient, but also on its refractive indices for the involved waves, for comparison of different nonlinear crystal materials one often uses a figure of merit like deff2 / (n1 n2 n3) .

**How are optical intensities affect a nonlinear crystal?**

Excessive optical intensities during operation may instantly damage a crystal. Unfortunately, nonlinear crystals often need to be operated not far from their optical damage threshold in order to achieve a sufficiently high conversion efficiency. This implies a trade-off between conversion efficiency and crystal lifetime.