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Encyclopedia > Pockels effect

The Pockels effect, or Pockels electro-optic effect, produces birefringence in an optical medium induced by a constant or varying electric field. It is distinguished from the Kerr effect by the fact that the birefringence is proportional to the electric field, whereas in the Kerr effect it is quadratic in the field. The Pockels effect occurs only in crystals that lack inversion symmetry, such as lithium niobate or gallium arsenide and in other noncentrosymmetric media such as electric-field poled polymers or glasses. A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... The Kerr effect or the quadratic electro-optic effect is a change in the refractive index of a material in response to the intensity of an external electric field. ... Figures with the axes of symmetry drawn in. ... Lithium niobate (LiNbO3) is a compound of niobium and lithium. ... This article is about the chemical compound. ...


Friedrich Carl Alwin Pockels studied the effect which bears his name in 1893. Friedrich Carl Alwin Pockels (1865 - 1913) was a German physicist. ... Year 1893 (MDCCCXCIII) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Tuesday of the 12-day slower Julian calendar). ...


Pockels cells

The Pockels effect is used to make Pockels cells, which are voltage-controlled wave plates. A wave plate is an optical device that alters the polarization state of a light wave travelling through it. ...


The electric field can be applied to the crystal medium either longitudinally or transversely to the light beam. Longitudinal Pockels cells need transparent or ring electrodes. Transverse voltage requirements can be reduced by lengthening the crystal.


Alignment of the crystal axis with the ray axis is critical. Misalignment leads to birefringence and to a large phase shift across the long crystal. This leads to polarization rotation if the alignment is not exactly parallel or perpendicular to the polarization. A transverse cell consists of two crystals in opposite orientation, which give a zero order wave plate when voltage is turned off. This is often not perfect and drifts with temperature. But the mechanical alignment of the crystal axis is not so critical and is often done by hand without screws; while misalignment leads to some energy in the wrong ray (either e or o -- for example, horizontal or vertical), in contrast to the longitudinal case, the loss is not amplified through the length of the crystal. In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... When polarized light is passed through a substance containing chiral molecules (or nonchiral molecules arranged asymmetrically), the direction of polarization can be changed. ...


Pockels cells may be used to rotate the polarization of a passing beam. See Applications below for uses.


Because of the high dielectric constant of the crystal, Pockels cells behave like a capacitor. When switching these to high voltage a high charge is needed; consequently, fast switching requires large currents. Pockels cells for fibre optics may employ a travelling wave design to reduce current requirements. Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...


Applications of Pockels cells

Pockels cells are used in a variety of scientific and technical applications:

  • A Pockels cell, combined with a polarizer, can be used for a variety of applications. Switching between no optical rotation and 90° rotation creates a fast shutter capable of "opening" and "closing" in nanoseconds. The same technique can be used to impress information on the beam by modulating the rotation between 0° and 90°; the exiting beam's intensity, when viewed through the polarizer, contains an amplitude-modulated signal.
  • Preventing the feedback of a laser cavity by using a polarizing prism. This prevents optical amplification by directing light of a certain polarization out of the cavity. Because of this, the gain medium is pumped to a highly excited state. When the medium has become saturated by energy, the Pockels cell is switched, and the intracavity light is allowed to exit. This creates a very fast, high intensity pulse. Q-switching, chirped pulse amplification, and cavity dumping use this technique.
  • Pockels cells can be used for quantum key distribution by polarizing photons.
  • Pockels cells in conjunction with other EO elements can be combined to form electro-optic probes.
  • A Pockels Cell was used by MCA Disco-Vision (DiscoVision) engineers in the optical videodisc mastering system - light from an Argon-Ion laser was passed through the Pockels Cell to create pulse modulations corresponding to the original FM video and audio signals to be recorded on the master videodisc. MCA used the Pockels Cell in videodisc mastering up until the sell-out to Pioneer Electronics. To increase the quality of the disc recordings, MCA patented a Pockels Cell stabilizer that reduced the 2nd Harmonic Distortion that could be created by the Pockels Cell during mastering. MCA used either a DRAW (Direct Read After Write) mastering system or a Photoresist system. The DRAW system was their originally preferred embodiment since it allowed non-clean room conditions during disc recording and instant checking of the disc quality during mastering. The original single-sided test pressings from 1976/77 were mastered with the DRAW system as were the "educational", non-feature titles at the formats release in December of 1978.

To help compare orders of magnitude of different times this page lists times between 10−9 seconds and 10−8 seconds (1 nanosecond and 10 nanoseconds) See also times of other orders of magnitude. ... In physics, intensity is a measure of the time-averaged energy flux. ... Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... It has been suggested that this article or section be merged with Feedback loop. ... Experiment with a laser (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: Light Amplification by Stimulated Emission of Radiation. ... A cavity resonator uses resonance to amplify a wave. ... A polarizer is a device that converts an unpolarized or mixed-polarization beam of electromagnetic waves (e. ... A laser system generally consists of three important parts: An energy source (usually referred to as the pump or pump source); A gain medium or laser medium; A mirror, or system of mirrors, forming an optical resonator. ... Q-switching, sometimes known as giant pulse formation, is a technique discovered circa 1962 by R.W. Hellwarth and F.J. McClung using electrically switched Kerr cell shutters and is a technique by which a laser can be made to produce a pulsed output beam. ... Chirped pulse amplification (CPA) or optical parametric chirped pulse amplification, is a technique for amplifying an ultrashort laser pulse up to the petawatt level with the laser pulse being stretched out temporally and spectrally prior to amplification. ... Q-switching, sometimes known as giant pulse formation, is a technique discovered circa 1962 by R.W. Hellwarth and F.J. McClung using electrically switched Kerr cell shutters and is a technique by which a laser can be made to produce a pulsed output beam. ... Quantum cryptography is an approach to securing communications based on certain phenomena of quantum physics. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Pioneers LaserDisc Logo The Laserdisc (LD) was the first commercial optical disc storage medium, and was used primarily for the presentation of movies. ...

See also

  • Electro-optic modulator
  • Acousto-optic modulator

  Results from FactBites:
 
Electro-optic effect - Wikipedia, the free encyclopedia (397 words)
The electro-optic effect is a change in the optical properties of a material in response to an electric field that varies slowly compared with the frequency of light.
Pockels effect (or linear electro-optic effect): change in the refractive index linearly proportional to the electric field.
Kerr effect (or quadratic electro-optic effect, QEO effect): change in the refractive index proportional to the square of the electric field.
Pockels effect - Wikipedia, the free encyclopedia (543 words)
It is distinguished from the Kerr effect by the fact that the birefringence is proportional to the electric field, whereas in the Kerr effect it is quadratic in the field.
Pockels cells may be used to modulate the phase of a passing beam.
If the Pockels cell is rotated 45° with respect to the polarization of the light, this leads to rotation of the polarization of a light beam by 90°.
  More results at FactBites »

 
 

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