The Kerr effect

The Kerr effect, also called the quadratic electro-optic effect, is a phenomenon in nonlinear optics where the refractive index of a material changes in response to an applied electric field. This change is proportional to the square of the electric field strength. Discovered by John Kerr in 1875, it is described by the equation:

Δ𝑛=𝐾⋅𝐸2 Δn=K⋅E 2

Here, Δ 𝑛 Δn is the change in refractive index, 𝐾 K is the Kerr constant (a property of the material), and 𝐸 E is the electric field.

The effect arises because the electric field induces polarization in the material, altering how light propagates through it. The Kerr effect is widely used in technologies such as:

• Optical modulators and switches: These control light intensity or phase, crucial in telecommunications and data transmission.
• Nonlinear optics applications: It contributes to phenomena like self-focusing, soliton formation, and wave mixing.

For example, if a material with a Kerr constant of 2×10⁻¹⁴m²/V² is exposed to an electric field of 5×10⁵ V/m, the refractive index would change by 5×10⁻³, demonstrating the effect's sensitivity to field strength​.

Tags: RP PHOTONICS, MODERN PHYSICS INSIGHTS, ELECTROMAGNETICS