Kerr electro-optic effect
in physics, the inducement of double refraction of light in a
transparent substance when a strong electric field is applied in a
direction transverse to the beam of light. In double refraction, the index
of refraction (a measure of the amount the ray is bent on entering the
material), and hence the wave velocity of light vibrating in the direction
of the electric field, is slightly different from the index of refraction
of the vibration perpendicular to it. Optically, the substance behaves
like a crystal with its optic axis parallel to the electric field. This
effect was discovered in the latter part of the 19th century by a Scottish
physicist, John Kerr. The same behaviour in solids is sometimes called the
Pockels effect.
 Arrangement for an optical shutter, operating by the Kerr effect |
The Kerr cell, also
referred to as a Kerr electro-optical shutter, is a device employing the
Kerr effect to interrupt a beam of light up to 1010
times per second. Linearly polarized light (light vibrating in one plane,
as shown in the Figure) is
passed through a liquid, such as nitrobenzene, contained in a cell with
transparent walls. The beam of light is intercepted by another polarizer
(analyzer in this case) set at 90
to the plane of polarization. When an electric potential is placed across
two plates straddling the light beam at 45
with respect to the plane of polarization, the plane-polarized light is
resolved into two components parallel and perpendicular to the electric
field. The light beam emerges from the cell circularly polarized because
the two components travel with different speeds and thus have a phase
difference. Consequently, the beam will be partially transmitted by the
analyzer. The Kerr cell has been employed in the photography of transient
phenomena, in measuring the speed of light, and is useful in laser and
communication studies.
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Kerr electro-optic effect (phys.)
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